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Glossary

A

Term What it means Where you met it
Action The last part of a data story: what the reader should do, starting with a verb. Unit 4 · Superset vs Power BI, and data storytelling
Admin The Superset role that can do everything, including granting rights and changing other people's dashboards. Unit 4 · Publishing and permissions
Aggregate function A function that reads many rows and returns one value: COUNT, SUM, AVG, MIN, MAX. Unit 1 · SQL Lab: groups
Alias A name you choose inside a query: AS n for a result column, AS p for a table. Valid in that query only. Unit 1 · SQL Lab: groups
Alpha The Superset role of a trusted builder: sees all data sources, but only alters what it owns and cannot grant rights. Unit 4 · Publishing and permissions
Annotation A mark you add on top of the data, such as a reference line or a labelled date, so the reader has something to compare with. Unit 3 · Configuring charts in Superset
Anscombe's quartet Four tiny datasets (Frank Anscombe, 1973) with almost the same summary statistics and four completely different charts. The reason you always draw the data. Unit 1 · Data do not speak alone
Apache Superset An open-source web application that connects to databases, asks them questions in SQL and draws the answers as charts and dashboards. The game client of this course. Unit 1 · Data sources
API A web address that answers with data instead of a web page. A trader: you ask, it answers. Unit 1 · Data sources
API key A password for programs: a long code a service gives you so it knows who is asking. Unit 1 · Data sources
Apparent duplicate Two rows that share a name but are different things, like the three games called Dark Matter. They will not stack. Unit 2 · Cleaning: units and duplicates
Applied Steps The list of every transformation done to a table in Power Query, in order. The notebook on the kitchen wall: the recipe of your cleaning. Unit 2 · Power Query
Assessment criterion One concrete check inside a learning outcome — an objective inside the quest. Each RA has three: a), b), c). Learning outcomes
Audience The specific person or group a dashboard is made for; change the audience and the dashboard changes, even with the same data. Unit 4 · Dashboards and KPIs
Average The sum of the values divided by how many there are; AVG in SQL. Unit 1 · SQL Lab: groups

B

Term What it means Where you met it
Bar chart One bar per category, bar length = the metric. The leaderboard: it answers "which category is bigger?" Unit 3 · Bar and line charts
Big number A chart that shows one single value, as large as possible. The final score on the stats screen. Unit 3 · Pie, heatmap and others
Bin One group of a numeric column, with a lower and an upper edge (5 to 15). Also called a band. Unit 2 · Categorisation
Branch One WHEN ... THEN ... line of a CASE. A row takes the first branch whose condition is true. Unit 2 · Categorisation

C

Term What it means Where you met it
Calculated column A new column worked out row by row, using only that row: the line total of the receipt (owners_min * price). Unit 2 · Synthetic variables
Card The Power BI visual that shows one big number. Superset calls it a Big Number. Unit 4 · Reports with Power BI
Casting The furnace: converting a value to another type with CAST(x AS type) or x::type. It works, or it stops with an error. Unit 2 · Cleaning: types and formats
Categorising Replacing many different values by a few labels, in a new column next to the original. Unit 2 · Categorisation
Category A label that puts a value into a group, like the rarity of an item: a number made readable. Unit 2 · Categorisation
Causation Changing one thing makes another change. A chart alone cannot prove it. Unit 3 · Histogram and scatter plot
Character code The number a computer stores for each character; what you see on screen is only how that number is drawn. Unit 2 · Cleaning: units and duplicates
Chartjunk Tufte's name for ink that shows no data: 3D effects, heavy gridlines, background pictures. Unit 3 · Visual perception
Check row One SELECT with the count, MIN, MAX and number of NULL that proves a conversion did what you meant. Unit 2 · Cleaning: types and formats
Cherry-picked range A start or end date chosen because it produces the headline, not because the question asks for it. The crop of photo mode. Unit 3 · Misleading charts
Comparison The "which one has more?" job: one category and one number, drawn as a bar chart. Unit 3 · Choosing the right chart
Comparison operator The sign that compares two values in a condition: =, <>, >, >=, <, <=. Unit 1 · SQL Lab: filters
Composition The "what share of the whole is each part?" job: a pie with five parts or fewer, sorted bars with more. Unit 3 · Choosing the right chart
Condition A yes-or-no question asked to every row, one by one; WHERE keeps the rows that answer yes. Unit 1 · SQL Lab: filters
Connection The set of details one program needs to reach a database server and be let in: host, port, database, user, password. Unit 1 · Connecting Superset to a database
Connection string One line of text holding every detail of a connection, password included. Treat it as a secret. Unit 1 · Connecting Superset to a database
Connector The piece of Power BI that knows how to talk to one kind of source. A driver with a form in front. Unit 1 · Getting data with Power BI
Context The first part of a data story: who is reading and what they have to decide. Unit 4 · Superset vs Power BI, and data storytelling
Correlation A number from −1 to 1 that says whether two columns rise together in a straight-line way. 0 means no straight-line link. Unit 1 · Data do not speak alone
CREATE TABLE AS Runs a query once and stores its result as a new table: the tupperware. Fast, but as old as the day you cooked it. Unit 1 · Datasets and destination
Credentials What you show to prove who you are: a user name and password, or an API key. Unit 1 · Data sources
Cross-filtering Clicking a part of a chart (a slice, a bar) to filter the other charts of the dashboard by that value. Unit 4 · Filters and cross-filters
CSV A table written as plain text: one line per row, a separator between values. Readable in any text editor. Unit 1 · Data sources

D

Term What it means Where you met it
D3 format The small standard language the number format codes come from. Unit 3 · Configuring charts in Superset
Dashboard A single screen that groups the few charts and numbers one audience needs to follow one subject and act on it: the HUD of your data. Unit 4 · Dashboards and KPIs
Dashboard (Power BI) A single page of tiles pinned from reports, only in the Power BI service, and it cannot be sliced. Not the same as a Superset dashboard. Unit 4 · Reports with Power BI
Data Raw recorded facts: a number, a word, a date. On their own they answer nothing. Unit 1 · Data do not speak alone
Data audit Opening the loot chest before you smelt: inspecting a table and counting what is wrong, without changing anything. Unit 2 · Data quality
Data lifecycle The path data takes from its source to the reader: obtain, prepare, analyse, represent. The module follows it in order. Learning outcomes
Data quality How far you can trust a table to answer your question: values present, correct, written one way and not repeated. Unit 2 · Data quality
Data source Any place data come from: a database, a file, a web service. Unit 1 · Data sources
Data storytelling Turning a finding into a message for a specific reader: the quest marker on top of the minimap. Unit 4 · Superset vs Power BI, and data storytelling
Data type The kind of value a column holds (text, whole number, exact decimal, date). It decides what you can do with it. Unit 2 · Cleaning: types and formats
Database server A program that keeps data in tables and answers questions about them. The game server; PostgreSQL is ours. Unit 1 · Connecting Superset to a database
Data-ink ratio The share of a chart's ink that actually shows data (Tufte, 1983). Erase the rest. Unit 3 · Visual perception
Datasaurus Dozen Thirteen datasets (Matejka and Fitzmaurice, 2017) with nearly identical statistics; one of them draws a dinosaur. Unit 1 · Data do not speak alone
Dataset Superset's name for "something I can build charts from". Unit 1 · Connecting Superset to a database
Decimal separator The symbol that marks where the whole part of a number ends: a point in English, a comma in Spanish. Unit 2 · Cleaning: types and formats
Dependent filter A filter whose list of values is cut down by the choice made in another filter. Unit 4 · Filters and cross-filters
Descriptive report The store page of a dataset: a short text saying what is in it, where it comes from, how good it is and what it cannot be used for. Unit 2 · The descriptive report
Destination The place where extracted data ends up stored, ready for the next step: here, a table in PostgreSQL. Unit 1 · Datasets and destination
Dimension What a chart groups by: the GROUP BY column. The player names on the leaderboard. Unit 3 · Bar and line charts
DirectQuery The Power BI mode that leaves the data in the database and asks again every time a chart needs them. The recipe. Unit 1 · Getting data with Power BI
Dirt inventory The written result of an audit: one line per problem with its column, kind of dirt, evidence (a number) and decision. Unit 2 · Data quality
Distribution How the values of a column are shared out: which are common and which are rare. Unit 2 · Exploratory statistics
Domain knowledge What you know about the real world behind the data (on Steam, no price means free to play). No query gives it to you. Unit 2 · Imputation
Draft A dashboard still being built: only its owners and the admins can see it, like a game server that is still private. Unit 4 · Publishing and permissions
Driver A small piece of software that lets one program talk to one kind of database. The translator. Unit 1 · Connecting Superset to a database
Dual axes Two series drawn with two different Y scales; where the lines cross depends on the scales, not on the data. Unit 3 · Misleading charts
Duplicate The same real thing recorded in more than one row: the same item twice in the chest. Unit 2 · Data quality

E

Term What it means Where you met it
Edge The value where one bin ends and the next begins. You choose it, so you write it down. Unit 2 · Categorisation
Edit mode The "customise HUD" screen of a dashboard: you drag, resize, add and delete pieces, and nothing is kept until you press Save. Unit 4 · Building a dashboard in Superset
Encoding (text) The rule that turns letters into the bytes stored in a file. Guess it wrong and Calvià becomes CalviÃ. Unit 1 · Data sources
Encoding (visual) The translation of a number into something you can see: a position, a length, an angle, a shade. Unit 3 · Visual perception
Encryption Scrambling what travels over the network so that only the two ends can read it. Unit 1 · Getting data with Power BI
Evolution The "how has it changed over time?" job: one date and one number, drawn as a line chart. Unit 3 · Choosing the right chart
Exploratory statistics Describing a column with a handful of numbers (centre, spread, shape) before you draw or conclude anything. Unit 2 · Exploratory statistics
Explore view The Superset screen where a chart is built: dataset panel, Data tab, Customize tab, chart and results. Unit 3 · Bar and line charts

F

Term What it means Where you met it
Field well A labelled box in the Visualizations pane (Values, X-axis, Y-axis) where you drop a field to tell a visual what to draw. Unit 4 · Reports with Power BI
Filter bar The strip on the left of a Superset dashboard where the filters live. Unit 4 · Filters and cross-filters
Filter (native filter) A control on the dashboard that lets the reader keep only some rows; Superset writes a WHERE into every chart in its scope. Unit 4 · Filters and cross-filters
Flag column A true/false column that remembers something about the row, like the note in the markbook margin: "this value was empty". Unit 2 · Imputation
Flatten Turn nested JSON into plain rows and columns. Unit 1 · Datasets and destination
Format The way a value is written down: Nov 16, 2004 and 16/11/2004 are two formats of one date. Unit 2 · Data quality
Frequency table The range of a column cut into boxes of equal width, with a count of the rows in each box. Unit 2 · Exploratory statistics

G

Term What it means Where you met it
Gallery A page with every chart you made, in the order you made them; the opposite of a dashboard, which starts from the reader's question. Unit 4 · Dashboards and KPIs
Gamma The Superset role of a reader: only sees charts and dashboards built on datasets it has been given access to. Unit 4 · Publishing and permissions
Generated column A column the database computes by itself from other columns of the same row, and keeps up to date (release_year from release_date). Unit 2 · Synthetic variables
Grid The invisible ruler of a dashboard canvas: each row is 12 columns wide and every chart is a whole number of columns. Unit 4 · Building a dashboard in Superset
GROUP BY Deals the rows into piles, one per different value of a column, and returns one result row per pile. Unit 1 · SQL Lab: groups

H

Term What it means Where you met it
HAVING A filter for whole piles, applied after they are counted. WHERE filters cards before the piles exist. Unit 1 · SQL Lab: groups
Header The first line of a CSV file, holding the column names. Unit 1 · Data sources
Heatmap A grid of two dimensions where the colour of each cell shows a metric. For patterns, not exact values. Unit 3 · Pie, heatmap and others
Hidden character Any character you cannot tell apart by eye: a non-breaking space, a tab, a line break stuck to a value. Unit 2 · Cleaning: units and duplicates
Histogram A chart that cuts one numeric column into equal bins and counts the rows in each. The rank distribution of ranked mode. Unit 3 · Histogram and scatter plot
Host The network name or address of the machine where a database server runs. Which server you join. Unit 1 · Connecting Superset to a database
HUD Heads-up display: the health bar, minimap and counters of a game, built to be read in a glance. Our model for a good chart. Unit 3 · Visual perception

I

Term What it means Where you met it
Import The Power BI mode that copies the data into the report file. The tupperware. Unit 1 · Getting data with Power BI
Imputation Deciding what value, if any, stands in for a missing one, and writing the decision down. Unit 2 · Imputation
Imputation log The written record of every imputation decision: column, how much was missing, what you did and why. Unit 2 · Imputation
Information What you get when somebody organises data to answer a question. Unit 1 · Data do not speak alone
INNER JOIN A join that keeps only the rows that found a partner. Rows with no partner vanish without an error. Unit 1 · SQL Lab: joins
Insight A finding with a number and a consequence: it changes what the reader decides. "Releases per year" is a label, not an insight. Unit 4 · Superset vs Power BI, and data storytelling

J

Term What it means Where you met it
Join Clipping the rows of two tables together into one wide row, matched by a condition written after ON. Unit 1 · SQL Lab: joins
JSON Labelled, nested text. Semi-structured: every value has a label, but records need not have the same fields. Unit 1 · Data sources

K

Term What it means Where you met it
Key The column two tables share, which tells you which row of one belongs to which row of the other. Unit 1 · SQL Lab: joins
KPI Key performance indicator: a number with a definition, a unit and a decision behind it. Unit 4 · Dashboards and KPIs

L

Term What it means Where you met it
Layout element A dashboard box that holds no data and organises or explains the charts: header, row, column, tabs, text / Markdown, divider. Unit 4 · Building a dashboard in Superset
Learning outcome (RA) Resultat d'aprenentatge — one skill you must be able to show by the end of the module. A quest in the quest log. This module has three. Learning outcomes
Least privilege Give each user the smallest set of rights that lets them do their job, and nothing more (Saltzer and Schroeder, 1975). Unit 4 · Publishing and permissions
LEFT JOIN A join that keeps every row of the table written first; rows with no partner get NULL in the other table's columns. Unit 1 · SQL Lab: joins
Legend The key that says which colour is which series. Off with one series, on (and on top) with several. Unit 3 · Configuring charts in Superset
Licence The text that says what you may do with data somebody else published. With CC BY: use them, but credit the source. Unit 1 · Data sources
Lie factor Tufte's 1983 measure: the effect shown in the chart divided by the effect in the data. Honest is close to 1. Unit 3 · Misleading charts
Limit One thing your data cannot tell, written next to the claim it affects. Unit 4 · Superset vs Power BI, and data storytelling
Limits The questions a dataset cannot answer and the conclusions it does not support. The system requirements of the store page. Unit 2 · The descriptive report
Line chart One point per moment in time, joined by a line. The match timeline: it answers "how did it change over time?" Unit 3 · Bar and line charts
Locale The regional conventions a computer uses to read and write values: decimal mark, date order, month names. Why 9.99 is not the same number on every PC. Unit 2 · Power Query
localhost A special host name meaning "this same machine": the one where the program using the word runs. Also written 127.0.0.1. Unit 1 · Connecting Superset to a database
Logical operator AND (both conditions must be true) and OR (one is enough). AND binds first, so use brackets when you mix them. Unit 1 · SQL Lab: filters
Lookup table A small table that explains a code: generations says that generation 5 is Unova, 2010. Unit 1 · SQL Lab: joins
Loud error An error that stops the query and names the value it could not convert. The good kind: you cannot miss it. Unit 2 · Cleaning: types and formats

M

Term What it means Where you met it
M The language in which Power Query writes down your steps. Every click adds one line of M. Unit 2 · Power Query
Markdown A simple way to format text with plain characters (**bold**); used for the notes on a dashboard. Unit 4 · Building a dashboard in Superset
Mean The average: one number for "a typical value" of a column. Unit 1 · Data do not speak alone
Median The value of the one standing in the middle when the data queues up from smallest to largest. Extreme values do not move it. Unit 2 · Exploratory statistics
Metric A named aggregate saved in a dataset: many rows in, one value per group out. The TOTAL of the receipt. Unit 2 · Synthetic variables
Misleading chart A chart where every number is true and the picture still leads to a wrong conclusion. Photo mode for data. Unit 3 · Misleading charts
Missing at random Blanks that are equally likely in any row. When they pile up in one group they are not missing at random, and filling them invents data. Unit 2 · Imputation
Missing value An empty slot in the chest: a cell with no value at all, written NULL in SQL. Not zero, not an empty word. Unit 2 · Data quality

N

Term What it means Where you met it
Nested Data inside data: a list of types inside the JSON answer for one Pokémon. Unit 1 · Datasets and destination
Non-breaking space A character (code 160, U+00A0) that looks exactly like a space but is not one: TRIM and ' ' do not touch it. Unit 2 · Cleaning: units and duplicates
Normalise (heatmap) Change what each cell's colour is compared with: the whole grid, its own column or its own row. The data stay the same. Unit 3 · Pie, heatmap and others
Normalising Giving a column one type, one format and one unit, so every value is written the same way. Unit 2 · Cleaning: types and formats
NULL The database's way of saying "there is no value here". Unit 1 · Connecting Superset to a database
Number format A short code (,d, .1%, $,.2f) that tells the chart how to write a number. It never changes the number itself. Unit 3 · Configuring charts in Superset

O

Term What it means Where you met it
Open data Data published so anyone can download, reuse and share it — under a licence that says how. Resources
Open source Software whose code is public: anyone may use it, study it and improve it for free. Unit 1 · Data sources
Outlier A value far away from all the others. One is enough to drag an average or a trend line. Unit 1 · Data do not speak alone
Owner A user who may edit a dashboard. You own the ones you create. Unit 4 · Publishing and permissions

P

Term What it means Where you met it
Pagination Splitting a long API answer into pages; a field such as next points to the following one. Unit 1 · Datasets and destination
Parameter An extra instruction after the ? in an API address, such as limit=20. Unit 1 · Datasets and destination
PARTITION BY The GROUP BY of a window: it splits the rows into groups, but the rows stay. Unit 2 · Synthetic variables
.pbix file A Power BI report saved on disk: its charts and, very often, a copy of the data. The fridge. Unit 1 · Getting data with Power BI
Percentile A position in the queue given as a fraction: 0.5 is the middle, 0.25 a quarter of the way in. Unit 2 · Exploratory statistics
Permalink A permanent link that remembers the state of a dashboard. An address, not a key: it carries no rights. Unit 4 · Publishing and permissions
Permission One single right: see this menu, read this dataset. Permissions are packed into roles. Unit 4 · Publishing and permissions
Physical dataset A dataset that points at a table in the database: a label on the jar, not a copy. Unit 1 · Datasets and destination
Pie chart A circle cut into slices that are parts of one whole. Fine with few, clearly different slices; otherwise use bars. Unit 3 · Pie, heatmap and others
Pop-out The effect of one mark standing out at a glance because it is the exception. Unit 3 · Visual perception
Port A numbered door on a machine. PostgreSQL usually waits behind 5432. Unit 1 · Connecting Superset to a database
Power BI Microsoft's commercial family of tools for turning data into charts and reports. Power BI Desktop runs only on Windows. Unit 1 · Getting data with Power BI
Power Query The part of Power BI that prepares data before you use it: it connects to a source, then cleans and reshapes the table step by step. Unit 2 · Power Query
Power Query Editor The window where you see a preview of your table and apply transformations to it. You open it with Transform Data. Unit 2 · Power Query
Preattentive attribute A visual property (colour, size, position, shape) the eye detects in a glance, before conscious attention. Unit 3 · Visual perception
Proprietary Software owned by a company that keeps the code and sets the conditions of use. Power BI is proprietary. Unit 4 · Superset vs Power BI, and data storytelling
Published A dashboard its author has declared ready. It means "no longer a draft", not "public": readers still need a login and access to the dataset. Unit 4 · Publishing and permissions
Purpose The decision a dashboard helps its audience take; one purpose per dashboard. Unit 4 · Dashboards and KPIs

Q

Term What it means Where you met it
Quartiles The three cuts that split the queue into four parts with the same number of rows: Q1 at 25%, the median at 50%, Q3 at 75%. Unit 2 · Exploratory statistics
Query One question asked to a database, written in SQL. Unit 1 · Connecting Superset to a database

R

Term What it means Where you met it
Rate limit The maximum number of questions an API accepts in a given time. Unit 1 · Data sources
Reference A pointer to something that lives elsewhere, like a shortcut: a dashboard points at a chart instead of copying it. Unit 4 · Building a dashboard in Superset
Regression line The straight line that passes closest to all the points of a scatter plot: the trend. Unit 1 · Data do not speak alone
Relational database Data stored in linked tables, kept by a server program such as PostgreSQL and asked in SQL. A vault on a server. Unit 1 · Data sources
Relationship The "when one goes up, does the other?" job: two measured numbers, drawn as a scatter plot. Unit 3 · Choosing the right chart
Report canvas The white page in Power BI Desktop where you place and arrange your visuals. Unit 4 · Reports with Power BI
Report (Power BI) One or more pages of visuals you can filter and slice. It is what Superset calls a dashboard. Unit 4 · Reports with Power BI
Reproducible A report is reproducible when another person, with only what you wrote, can get the same data and reach the same numbers. Unit 2 · The descriptive report
Role A named bundle of permissions given to users: the rank on the game server. Superset ships Admin, Alpha and Gamma. Unit 4 · Publishing and permissions

S

Term What it means Where you met it
Scatter plot A chart where each row becomes one dot: x says how far right, y says how far up. Unit 1 · Data do not speak alone
Schema A folder of tables inside a database. Ours is public. Unit 1 · Connecting Superset to a database
Scope The set of charts a filter reaches; a chart outside the scope ignores the filter. Unit 4 · Filters and cross-filters
Screenshot test Could a stranger read your chart alone, with no caption and nobody to ask? If not, it is not finished. Unit 3 · Configuring charts in Superset
Semantic model Power BI's name for the data behind a report: tables, their relationships and calculations. Close to a Superset dataset. Unit 4 · Reports with Power BI
Semi-structured data Data where every value has a label but the shape can change from one record to the next, like JSON. Unit 1 · Data sources
Separator The character between one value and the next in a CSV file (also called delimiter). Usually , or ;. Unit 1 · Data sources
Series One line, or one set of bars, in a chart. Unit 3 · Configuring charts in Superset
Share of the total What part of the whole one group is, as a percentage: COUNT(*) / SUM(COUNT(*)) OVER (). Unit 2 · Synthetic variables
Silent error A wrong value with no warning at all, like '04/11/2026'::date giving 11 April. The dangerous kind. Unit 2 · Cleaning: types and formats
Skewed A distribution where most values pile up on one side and a long tail of rare values stretches out on the other. Mean and median end up far apart. Unit 2 · Exploratory statistics
Slicer A Power BI filter that sits on the canvas as a visual: click a value and the other visuals on the page keep only the matching rows. Unit 4 · Reports with Power BI
Snapshot A copy of the data as it was at one moment. It does not update itself. Unit 1 · Datasets and destination
SQL Structured Query Language: the language for asking questions to a relational database. Unit 1 · Connecting Superset to a database
SQL Lab The page of Superset where you write a query, run it and see the answer as a table. Unit 1 · Connecting Superset to a database
Standard deviation Roughly, the typical distance between a value and the mean. A long tail inflates it. Unit 2 · Exploratory statistics
Structured data Data in fixed rows and columns: every row has the same fields. The inventory grid. Unit 1 · Data sources
Summary statistic One number that describes a whole column. The stats screen of a dataset: fast, but a compression. Unit 1 · Data do not speak alone
Symmetric A distribution whose two sides look roughly alike, like a hill. Mean and median are close together. Unit 2 · Exploratory statistics
Synthetic variable A column nobody collected: it is computed from the columns that were, like the line total on a receipt. Unit 2 · Synthetic variables

T

Term What it means Where you met it
Table (chart) Rows and columns of exact values. The right visualisation when the reader needs to look things up. Unit 3 · Pie, heatmap and others
Thousands separator The symbol that only groups digits so people can read them (1,234 or 1.234). Decoration to remove before a cast. Unit 2 · Cleaning: types and formats
Tile One pinned visual on a Power BI dashboard. Unit 4 · Reports with Power BI
Time grain The size of the time step on a line chart's X-axis (year, month...). The zoom of the timeline. Unit 3 · Bar and line charts
Time range filter A dashboard filter where the reader picks a start date (included) and an end date (excluded). Unit 4 · Filters and cross-filters
Trimming Cutting the spaces off both ends of a text with TRIM, so ' Valve ' and 'Valve' become the same publisher. Unit 2 · Cleaning: types and formats
True duplicate A row identical to another in every column: the same record twice, typically a file loaded twice. Unit 2 · Cleaning: units and duplicates
Truncated axis An axis that does not start at zero, so only the top of each bar is drawn and small gaps look huge. The zoom of photo mode. Unit 3 · Misleading charts
Type of question What the reader wants to do with the numbers: rank them, follow them in time, see how they spread, see if two move together, or split a whole into parts. The job that picks the tool. Unit 3 · Choosing the right chart

U

Term What it means Where you met it
Unit What a number counts or measures: dollars, minutes, people. A number without its unit can be read wrongly. Unit 2 · Cleaning: units and duplicates
Unstructured data Data with no fields at all, like a photo or a chat. A person understands it; a program cannot read "the price column". Unit 1 · Data sources

V

Term What it means Where you met it
Value filter A dashboard filter where the reader picks one or more values of a column from a list. Unit 4 · Filters and cross-filters
Variance A number that says how spread out the values are around the mean. Unit 1 · Data do not speak alone
View mode The finished dashboard as the reader sees it, with no building tools. Unit 4 · Building a dashboard in Superset
Virtual dataset A saved query that Superset runs again every time: the recipe. Always fresh. Unit 1 · Datasets and destination
Visual One chart, table or number on a Power BI report. Superset calls it a chart. Unit 4 · Reports with Power BI
Visual hierarchy (charts) The order in which the eye moves through a chart. You set it with size, colour and sorting. Unit 3 · Visual perception

W

Term What it means Where you met it
Wildcard A symbol in a LIKE pattern that stands for text you do not know: % is any text, _ is exactly one character. Unit 1 · SQL Lab: filters
Window function A calculation over a group of rows that writes its result next to every row without collapsing them. You spot it by the word OVER. Unit 2 · Synthetic variables
Work unit (UT) Unitat de treball — a block of classes on one topic. Each one trains one learning outcome. Learning outcomes

Missing a word you heard in class? Tell your teacher — new terms are added as the course moves on.