Tableau
95 flashcards by MentisLibrary
Building and reasoning about Tableau vizzes: dimensions and measures, chart choice, calculated fields, level of detail expressions, table calculations, the filter order of operations, parameters, actions, dashboards and publishing.
- What is the difference between a dimension and a measure?
- A dimension is a qualitative field that slices the data into categories; a measure is a numeric field that gets aggregated.
- What does the colour of a pill mean in Tableau?
- Blue means discrete, so the field produces headers; green means continuous, so the field produces an axis.
- What happens when you drop a measure on a shelf?
- Tableau aggregates it, defaulting to SUM, at the level of detail set by the dimensions in the view.
- What is the level of detail of a view?
- The combination of dimensions present in the view, which determines what one mark represents.
- What does the Detail shelf on the Marks card do?
- It adds a dimension to the view, splitting the marks more finely without drawing a header, an axis or a colour.
- What is a hierarchy?
- A stack of dimensions ordered from coarse to fine, drilled through with the plus and minus controls on the pill.
- What are Measure Names and Measure Values?
- Generated fields: Measure Names is a dimension listing every measure, and Measure Values is a placeholder holding the ones you use.
- What is a bin?
- A field that groups the values of a measure into equal-width buckets.
- What does ATTR() do?
- Returns the value of a field if it is the same for every underlying row of the mark, and an asterisk if it is not.
- What is a geographic role?
- An assignment that tells Tableau a field holds places, which generates Latitude and Longitude so it can be mapped.
- What does the Show Me panel do?
- Highlights the chart types the selected fields can produce and builds the chosen one for you.
- Which chart compares a measure across categories?
- A bar chart, which is the most accurate encoding for comparison because the eye compares lengths from a common baseline.
- When is a line chart the right choice?
- When the horizontal axis is continuous, above all time, so the line encodes change between points.
- How do you build a scatter plot?
- Put one measure on Columns and another on Rows, then add a dimension to Detail so the marks separate.
- How do you make a histogram?
- Create a bin from the measure, put the bin on Columns and a count on Rows.
- What does a box plot show?
- The median, the quartiles, and the whiskers reaching to the furthest point within 1.5 times the interquartile range, with points beyond drawn individually.
- What is a dual axis chart?
- Two measures drawn in one pane on their own axes, which can then be layered as different mark types.
- What does Synchronize Axis do?
- Forces both axes of a dual axis chart onto the same scale.
- When is a map the right chart?
- When the geographic pattern itself is the question, rather than the ranking of the places.
- What is a highlight table?
- A text table whose cells are coloured by the measure, so the numbers stay readable while the pattern appears.
- What does a treemap encode?
- Nested rectangles whose area is one measure and whose colour is usually another.
- How do you add a reference line?
- Drag Reference Line from the Analytics pane onto the axis, then choose the scope and value.
- Where do you write a calculated field?
- Analysis, Create Calculated Field, or the drop-down at the top of the Data pane.
- What is the difference between a row-level and an aggregate calculation?
- A row-level calculation runs on each underlying record before aggregation; an aggregate calculation runs on the aggregated values in the view.
- Why does Tableau say it cannot mix aggregate and non-aggregate arguments?
- Because every branch of a calculation must be at the same level: either all aggregated or all row level.
- IF versus CASE in a Tableau calculation
- CASE compares one expression against exact values; IF handles any condition, including ranges and compound tests.
- What does IIF do?
- Evaluates a test and returns one of two values, with an optional fourth value for unknown.
- What does ZN() do?
- Returns zero when its expression is null, and the value otherwise.
- IFNULL versus ISNULL
- IFNULL(a, b) returns b when a is null; ISNULL(a) returns a boolean saying whether a is null.
- How do you find the number of days between two dates?
- DATEDIFF(date_part, start_date, end_date).