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TEC-DATA85-07 · Lesson 7 · 14 clock hours · lab

Tableau Public: Calculations, Parameters, and Stories

Objective. Students build a Tableau Public workbook containing at least three coordinated views, one parameter control, one calculated field, and a two-slide story, then publish it to a personal Tableau Public profile.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by an industry-certified professional or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

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Tableau Public: Calculations, Parameters, and Stories

What Tableau Public Is and Why It Matters

Tableau Public is the free, browser-hosted version of Tableau Desktop. You download a desktop authoring application, connect to local files such as CSV spreadsheets, build interactive visualizations, and then publish finished workbooks to a personal profile on the Tableau Public website. Anyone with the URL can view and interact with your work in a browser—no Tableau license required. Because every published workbook is visible to the public, never upload data that contains personal, confidential, or proprietary information. Use only open, public datasets—exactly like the city open-data CSV provided for this lab.

Connecting to a CSV and Building the Three Core Views

When you open Tableau Public Desktop, choose Connect → Text File and select your CSV. Tableau reads column headers as either dimensions (categorical, shown in blue) or measures (numeric, shown in green). You can change a field's data type by right-clicking its pill in the Data pane.

Bar chart: Drag a categorical dimension (such as Neighborhood) to Columns and a numeric measure (such as Incident Count) to Rows. Tableau draws a horizontal or vertical bar chart automatically. Sort bars descending so the largest value appears first—this helps viewers read rank quickly.

Line trend: Drag a date field to Columns. Tableau aggregates by year by default; click the plus icon on the date pill to drill to month or quarter. Drag a measure to Rows. This view shows change over time and is the right chart type whenever your x-axis is continuous time.

Filled map: If your data contains geographic fields such as city, ZIP code, or latitude/longitude, Tableau assigns a geographic role automatically. Drag the geographic dimension to the canvas; Tableau switches to map view. Drag a measure to the Color card. The resulting choropleth (filled map) encodes value as color intensity—viewers immediately see which areas rank high or low.

Building the Dashboard and Linking Views with a Filter Action

A dashboard is a single canvas that holds multiple sheets. Click the new-dashboard icon at the bottom tab bar. Drag your three sheets from the Sheets panel onto the canvas. Resize each container by dragging its border.

A filter action makes the dashboard interactive: clicking a mark in one view automatically filters another view. To add one, go to Dashboard → Actions → Add Action → Filter. Set the source sheet to your map and the target sheet to your bar chart. Choose Select as the trigger and Show all values when the selection is cleared. Now when a user clicks a region on the map, the bar chart updates to show only data for that region. This is a core feature that transforms a static layout into an analytic tool.

Parameters and Calculated Fields

A parameter is a workbook-level variable that a user can change at runtime. Parameters are not connected to the data source directly; they hold a single value that other parts of the workbook can reference.

To create a Top N selector, right-click in the Data pane, choose Create Parameter, name it `Top N`, set the data type to Integer, and set the allowable values to a Range from 1 to 20 with a step of 1. Show the parameter control on the dashboard so the user sees a slider or input box.

A calculated field uses that parameter. Right-click in the Data pane, choose Create Calculated Field, and write a formula such as:

```

RANK(SUM([Incident Count])) <= [Top N]

```

Drag this Boolean field to the Filters card on your bar chart and keep only `True`. Now the bar chart shows exactly the number of bars the user selects with the slider.

To make the chart title update dynamically, double-click the sheet title and insert the parameter by clicking Insert → Parameters.Top N. The title might read: Top <Parameters.Top N> Neighborhoods by Incident Count. As the user moves the slider, the headline changes automatically—a small detail that greatly improves clarity.

An IF/THEN or CASE calculated field can also classify data. For example:

```

IF SUM([Incident Count]) > 500 THEN "High"

ELSEIF SUM([Incident Count]) > 200 THEN "Medium"

ELSE "Low"

END

```

Drag this field to Color to encode risk level without manual data editing.

Building a Two-Slide Story

A story in Tableau is a sequence of story points—individual slides that each display a dashboard or sheet, optionally with a caption and annotations. Stories guide an audience through an analysis the same way a slide deck does, but every view remains interactive.

Click the new-story icon at the bottom tab bar. Drag your dashboard onto the story canvas for slide 1. Add a caption summarizing the key insight. Use the Annotation → Mark tool (right-click a mark on the view) to pin a text label to a specific data point, explaining why it matters.

Click Blank to add slide 2. Drag the same or a different sheet onto the canvas. Use a highlight filter (set the filter action trigger to Highlight instead of Filter) to dim non-selected marks so the outlier stands out visually. Add a Text box from the Objects panel with a callout that names the outlier and states its significance.

Publishing to Tableau Public

When your workbook is complete, choose File → Save to Tableau Public As. You will be prompted to sign in with your Tableau Public account. After upload, Tableau opens your profile page in a browser; copy the URL and submit it as your deliverable.

Data privacy reminder: Tableau Public workbooks are visible to everyone on the internet. Always verify that your dataset contains no personally identifiable information (PII) before publishing. If a dataset included names, addresses, or any protected category, you must remove or aggregate those fields before upload—this is both an ethical obligation and, depending on jurisdiction, a legal one.

Lab Log and Accuracy Habits

Record every formula you write in your lab log. When you spot-check a calculated field, compute the expected result by hand for two or three rows of raw data and compare against what Tableau displays. This habit of manual verification is standard practice in data analytics and is tested by every certification in this program.

Key terms8

ParameterA workbook-level variable in Tableau that holds a single user-adjustable value (integer, float, string, or date) that other calculations and titles can reference at runtime.
Calculated FieldA new data column defined by a formula written in Tableau's calculation editor; it can use built-in functions, operators, and parameters to derive values not present in the original data source.
Filter ActionA dashboard-level action that uses a mark selection in one sheet as a filter applied to one or more other sheets, enabling coordinated, interactive views.
Story (Tableau)A Tableau sheet type that arranges a sequence of story points—each displaying a saved dashboard or sheet state with a caption—to guide an audience through a narrative analysis.
Filled Map (Choropleth)A map view in which geographic areas are shaded by color intensity to represent the magnitude of a numeric measure, allowing quick spatial comparison.
DashboardA Tableau canvas that combines multiple sheets, images, text boxes, and web objects into a single interactive layout for presentation or analysis.
AnnotationA text label anchored to a specific mark, point, or area on a Tableau view that provides explanatory context directly on the visualization.
Dimension vs. MeasureIn Tableau, dimensions are categorical fields (shown in blue) used to slice and group data; measures are numeric fields (shown in green) that Tableau aggregates with functions such as SUM or AVG.

Worked examples3

1. Write a Tableau calculated field that ranks neighborhoods by SUM of Incident Count and returns TRUE only for the top N, where N comes from a parameter named [Top N].
  1. Step 1 – Create the parameter: right-click the Data pane, choose Create Parameter, name it 'Top N', set data type Integer, allowable values Range 1–20, step 1.
  2. Step 2 – Open the calculated field editor: right-click the Data pane, choose Create Calculated Field, name it 'In Top N'.
  3. Step 3 – Enter the formula: RANK(SUM([Incident Count])) <= [Top N]
  4. Step 4 – Click OK. Drag 'In Top N' to the Filters card on the bar chart sheet and check only TRUE to keep the top-N bars.
  5. Step 5 – Verify manually: if [Top N] = 3 and the three neighborhoods with the highest SUM are A (900), B (750), C (600), those three should appear; neighborhood D (400) should be hidden.
Answer: The calculated field RANK(SUM([Incident Count])) <= [Top N] returns TRUE for every neighborhood whose rank (1 = highest) is less than or equal to the parameter value, correctly limiting the bar chart to the user-selected number of bars.
2. Write a Tableau IF/THEN calculated field that classifies each row by Incident Count into 'High', 'Medium', or 'Low', using thresholds of 500 and 200.
  1. Step 1 – Open the calculated field editor and name the field 'Risk Level'.
  2. Step 2 – Enter the formula: IF SUM([Incident Count]) > 500 THEN "High" ELSEIF SUM([Incident Count]) > 200 THEN "Medium" ELSE "Low" END
  3. Step 3 – Click OK and drag 'Risk Level' to the Color card on any sheet.
  4. Step 4 – Spot-check: for a neighborhood with SUM = 620, the formula evaluates 620 > 500 → TRUE → result is 'High'. For SUM = 350, 350 > 500 → FALSE, 350 > 200 → TRUE → result is 'Medium'. For SUM = 90, both conditions are FALSE → result is 'Low'.
Answer: The IF/THEN expression correctly assigns 'High' when SUM > 500, 'Medium' when SUM is 201–500, and 'Low' when SUM ≤ 200, verified by substituting sample values into each branch.
3. A bar chart currently shows all 15 neighborhoods. A student sets [Top N] to 5. How many bars should appear, and which rows from the table below are included? Table: Alpha 900, Beta 750, Gamma 600, Delta 400, Epsilon 350, Zeta 300 (only first 6 shown).
  1. Step 1 – Rank all neighborhoods by SUM descending: Alpha = 1, Beta = 2, Gamma = 3, Delta = 4, Epsilon = 5, Zeta = 6, …
  2. Step 2 – The calculated field RANK(SUM([Incident Count])) <= [Top N] evaluates <= 5.
  3. Step 3 – Alpha (rank 1): 1 ≤ 5 → TRUE. Beta (rank 2): TRUE. Gamma (rank 3): TRUE. Delta (rank 4): TRUE. Epsilon (rank 5): TRUE. Zeta (rank 6): 6 ≤ 5 → FALSE.
  4. Step 4 – From the six rows shown, five pass the filter. All remaining ten neighborhoods (ranks 7–15) also return FALSE and are hidden.
Answer: Five bars appear: Alpha, Beta, Gamma, Delta, and Epsilon. Zeta and all lower-ranked neighborhoods are excluded because their rank exceeds 5.
In class: Guided Tableau build: using a provided city open-data CSV, students connect the data, build a bar chart, a line trend, and a filled map, and arrange all three on a single dashboard with a filter action linking the map to the bar chart. · Parameter and calculated field lab: students create a numeric parameter (e.g., 'Top N selector') and a calculated field using an IF/THEN or CASE expression; they embed the parameter in a title so the chart headline updates dynamically when the user moves the slider. · Story point narrative: students add a two-slide story—slide 1 shows the default state with an annotation explaining the key insight; slide 2 highlights an outlier using a highlight filter and a callout text box—then publish to Tableau Public and submit the URL.
Materials: Tableau Public Desktop (free download), provided city open-data CSV, Tableau Public profile (free account), Tableau online help (help.tableau.com), lab log
Check: Instructor visits each student's published Tableau Public URL; pass requires working dashboard filter action, parameter that dynamically updates at least one view title, calculated field returning correct values verified against a spot-check formula, and two story slides with annotations. Google Data Analytics mapping: Create visualizations and communicate findings.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Google Data Analytics – Create visualizations and communicate findings
1. A student drags a date field to Columns and a measure to Rows in Tableau. Which chart type does Tableau create by default?
Microsoft PL-300 – Model data / create calculated fields
2. In Tableau, a parameter differs from a filter primarily because a parameter:
CompTIA Data+ – Data analysis and visualization
3. Which Tableau feature should you use to make a bar chart automatically show only the top N neighborhoods when a user moves a slider?
Google Data Analytics – Create visualizations and communicate findings
4. A student wants clicking a region on a filled map to automatically filter a bar chart on the same dashboard. Which Tableau feature accomplishes this?
IBM Data Science Professional – Data visualization and storytelling
5. What is the correct purpose of a Tableau story?
CompTIA Data+ – Data governance and quality
6. Before publishing a workbook to Tableau Public, the most important data-safety check is to verify that:
Microsoft PL-300 – Create calculated fields and measures
7. A student writes this calculated field: IF SUM([Sales]) > 1000 THEN "High" ELSEIF SUM([Sales]) > 500 THEN "Medium" ELSE "Low" END. For a row where SUM([Sales]) = 750, what value does the field return?
IBM Data Science Professional – Data visualization and storytelling
8. Which Tableau element lets you pin a text label to a specific data point on a view to explain why that point is significant?
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