Webbo3 Power BI · Cohort 1 · Day 13 of 16
Day 13: Building Visuals
Cards, bars, columns, lines, tables and matrices: which visual answers which question, and how to make each one easy to read.
By the end of today you can
- Choose the right visual for a question before you build it
- Build a card, a bar chart, a column chart, a line chart, a table and a matrix
- Format a visual so a manager can read it in five seconds
- Spot the three charts that mislead, and what to use instead
- Start Assignment 3, the one-page dashboard
Your measures are right. Now they need a face. A visual is a question answered in a picture, and the wrong picture hides a right answer.
Open your Day 12 file and add a new report page (the + at the bottom). Every visual today goes on it.
1. What a Visual Is
Definition
A visual is a chart, table or card on a report page. You build it by choosing a type in the Visualizations pane and dragging fields into its wells: the boxes labelled X-axis, Y-axis, Values, Rows, Columns and Legend. Measures go in Values; columns from dimension tables go on the axis, rows or legend.
Real-Life Example
A weather forecast. The temperature today is one big number. The week ahead is a row of icons. The rainfall over a year is a line. Same weather, three questions, three pictures.
Types: Pick by the Question
| The question sounds like | Visual | Why |
|---|---|---|
| "How much, in total?" | Card | One number, big |
| "Which is biggest?" | Bar chart | Long labels fit on the side; sorted bars rank at a glance |
| "How do a few groups compare, split by something?" | Clustered column chart | Side-by-side columns |
| "Is it going up or down over time?" | Line chart | The slope is the answer |
| "Show me the exact figures" | Table | Rows and numbers, nothing else |
| "Break it down two ways at once" | Matrix | Rows by columns, with totals |
Picture the forecast: one number for today, icons for the week, a line for the year.
2. The Card: "How Much?"
A card shows one measure as one number. Put the most important numbers on cards along the top of a page: the reader sees them first.
Click path
Display units matter. ₦145,854,226 is exact but slow to read; ₦145.9M is read in a glance. Keep the exact figure for tables.
3. The Bar Chart: "Which Is Biggest?"
Bars run sideways, so long names like "Independence Layout Filling Station" fit without tilting. Always sort by the value, largest at the top, so the ranking is the first thing seen.
Click path
GRA Filling Station leads and Lekki Filling Station trails. Nobody had to read a number to see it.
4. The Column Chart: "How Do a Few Groups Compare?"
Columns stand upright. They suit a few short categories, and they cope well with a Legend, which splits each column into side-by-side columns, one per legend value.
Click path
5. The Line Chart: "Going Up or Down?"
Time goes on the X-axis, always from the Date table, left to right. The slope of the line is the answer. Put Date[Year] in the Legend and you get one line per year.
Click path
Look at the 2023 line: about ₦3.1M a month until May, then a step up to ₦5.9M a month from June, the month the fuel subsidy went. The line did not climb slowly; it jumped, which tells you the cause was one event, not a trend. If the months come out Apr, Aug, Dec, you forgot Day 7's step: sort Month by Month Number.
6. Table and Matrix: "Show Me the Figures"
A table lists rows and columns of values, like Excel. A matrix adds a second grouping across the top, with totals both ways. Use them for detail under the charts, not instead of them.
Click path
7. Formatting: Five Seconds to Read
Select a visual, then the paintbrush (Format visual). Five changes make most visuals readable:
| Change | Where | Why |
|---|---|---|
| A title that says the finding | General, Title | "Lekki earns the most" beats "Sum of Revenue by Station" |
| Data labels on | Visual, Data labels | The reader does not have to guess from the axis |
| Display units | Data labels or Y-axis, Display units | ₦12.3M, not ₦12,345,678 |
| Sorted | ... More options, Sort axis | Rankings read top to bottom |
| One colour unless colour means something | Visual, Bars or Columns, Colors | Seven colours for seven stations say nothing |
8. Charts That Mislead
- A pie with many slices. Nobody can compare 18 slices. Pies are for two or three parts of a whole at most; otherwise use a sorted bar chart.
- A line through categories. A line joining Lekki to Wuse says there is a trend between stations. There is not. Lines are for time.
- A value axis that does not start at zero on a bar or column chart. It makes a small difference look huge. Leave the axis start on Auto or 0.
Fuel is 95% of revenue, so a pie is one big slice and two slivers you cannot read. A card saying "Fuel: 95% of revenue" says it better.
Build the same Total Revenue by Station twice: once as a pie chart, once as a sorted bar chart. Show both to someone who has not seen the data and ask which station is third. Time how long they take with each.
9. Assignment 3 Is Released
Assignment 3 asks for a one-page Webbo Oil dashboard: a KPI card, a bar chart, a trend line and a slicer. It is due on Day 15.
The full brief is on the Assignment 3 page, the next lesson in this course.
Do This Now
- Add a new page and build the three cards.
- Build the sorted bar chart of stations.
- Build the region and year column chart.
- Build the monthly line chart with a line per year.
- Build the station by year matrix.
- Give every visual a title that says what it shows, and turn on data labels.
- Read the Assignment 3 brief.
Checkpoint
Q1. "Which attendant sold the most?" Which visual?
A bar chart, sorted descending. It ranks, and names fit on the side.
Q2. "Is diesel revenue rising?" Which visual?
A line chart with months from the Date table on the X-axis, filtered to diesel.
Q3. When is a pie chart acceptable?
For two or three parts of a whole, when the point is one part's share.
Q4. Your line chart shows Apr, Aug, Dec in that order. What did you forget?
To sort Date[Month] by Date[Month Number].
Tick Before You Move On
- ☐ Three cards along the top, in display units
- ☐ A bar chart sorted largest first
- ☐ A line chart with months in calendar order
- ☐ A matrix with totals across and down
- ☐ Every visual has a title and data labels
Quick Recap
Choose the visual by the question: card, bar, column, line, table or matrix. Measures go in Values; dimension columns go on the axis, rows or legend. Sort bars, start value axes at zero, keep lines for time. Titles say the finding; display units make numbers quick to read. Assignment 3 is due on Day 15.
Final Scenario
Alhaji Musa Bello walks past your screen and stops.
He sees ₦145.9M on a card, the stations ranked in a bar chart, and a 2023 line that steps up in June. He reads the whole business in the time it takes to put his bag down, and asks only one question: "Is that jump more customers, or just the price?"
When the picture is right, the only questions left are about the business.
Next: the Assignment 3 brief, then the Day 14 lab.