Combo charts from Google Sheets to Slack, two metrics, one story (and one caveat)
Combo charts in Google Sheets mix bars and lines on the same chart. Chartcastr currently renders them as line charts. Here is what that means in practice and when it still works.
Combo charts from Google Sheets to Slack, two metrics, one story (and one caveat)
Combo charts in Google Sheets let you mix bars and lines on the same chart. The classic use case: spend (bars) and ROAS (line) on the same x-axis. The bars give you the absolute numbers. The line gives you the efficiency, often on a secondary y-axis.
It's a useful chart shape. It's also the one place where Chartcastr currently does something different from Sheets: we render combo charts as line charts. Both series come through. The bars become lines.
This post explains what that means and how to decide whether it's a problem for your team.
What you actually get
When you point Chartcastr at a Google Sheets combo chart:
- All series are preserved. If your combo had two bar series and a line series, all three series come through.
- All three render as lines.
- Colours, axis labels, legend position, and ranges come through unchanged.
For most "primary metric + secondary efficiency metric" use cases, all-lines is acceptable. You're still seeing the trajectory of both. The visual distinction between "this is a quantity" (bar) and "this is a rate" (line) is what gets lost.
When all-lines is fine
- Spend and ROAS, both as lines. Spend trending up, ROAS holding steady, the story reads.
- Revenue and conversion rate, both as lines. Same shape. Same readability.
- Sign-ups and activation rate, both as lines. Two lines, two stories.
The eye still picks up the slopes. The summary you write underneath the chart can name which is the volume metric and which is the rate.
When you really want bars
Combo charts shine when one of the metrics is small in count and large in importance, single-digit bars are easier to read at a glance than a flat line at the bottom of the chart. If that's your shape, the cleanest path right now is two separate charts:
- A bar chart for the count metric.
- A line chart for the rate metric.
- Schedule them to land in Slack together.
Two messages back-to-back tell the same story without compromising either visualisation.
Why we do it this way
Most combo charts we see in the wild are "primary metric on the left axis, secondary rate metric on the right axis". That shape reads well as two lines. The cases where bars are critical are a minority, and we'd rather render the data faithfully as two lines than guess at a hybrid that's hard to get right at small Slack-thumbnail sizes.
This may change. If you have a use case where bars are essential, tell us, we use those reports to prioritise.
Setting it up
- Build the combo chart in Google Sheets the way you'd normally build it.
- Connect it as a Chartcastr Google Sheets source.
- Pick a destination. Schedule it.
- Watch what shows up. If "two lines" reads fine, you're done. If not, split it.
The full mapping is documented in the Premade Charts docs. The line is "Combo Chart → Line Chart (Defaults to line)".
The companion read for time-based metrics is line charts in Slack, which goes deeper on what to plot and how often.
