Line charts from Google Sheets to Slack, trend tracking that survives Mondays
Line charts are the right shape for almost any time series. How to send them automatically from Google Sheets to Slack with Chartcastr, and what to put on the y-axis when you have more than one metric.
Line charts from Google Sheets to Slack, trend tracking that survives Mondays
Most metrics worth watching are time series. Revenue, sign-ups, MAU, error rate, spend, ROAS, all of them are some number, observed at regular intervals, that you'd like to know about at a glance.
A line chart is the default shape for that data. It's not the only shape, but if you're not sure, lines are almost always the right call.
Why lines, not bars, for time
Bars are for categorical comparisons. Lines are for change over time. The reason lines win for time is small but important: a line lets your eye trace the slope. Slope is the question, "is it going up or down, and how fast", and a line gives you the answer in one fixation.
A bar chart of weekly revenue forces your eye to compare heights one pair at a time. A line chart of the same data gives you the trajectory in a single read.
What to plot, and how many
One metric, one line is the easy case. Sign-ups per day, weekly active users, daily error count, single line, x-axis is time, y-axis is the metric.
Two related metrics is a judgement call. If they share a unit (clicks vs impressions, opens vs deliveries), one chart with two lines works. If they don't share a unit, you usually want either two charts or a combo chart with a secondary axis.
Three or more lines on one chart is almost always a mistake unless you're tracking the same metric across categories (per-region MRR, per-cohort retention). Beyond that the chart becomes a tangle and people stop reading.
A few patterns that work
- Last 30 days, daily. The default for anything you check in the morning.
- Last 12 weeks, weekly. For metrics that are noisy day-to-day but smooth weekly. Weekly active users is the canonical example.
- Year over year. Two lines: this year and last year, on the same axis. Reveals seasonality without you having to explain seasonality.
- Cumulative. New sign-ups summed since the start of the quarter. Better as an area chart most of the time, but lines work too.
What the Slack version looks like
The pattern most teams settle on:
- A single line chart in
#metrics(or#growth, or#finance) every weekday morning. - Optional AI summary that explains the slope: "MAU is up 6% week-over-week, mostly driven by the new sign-ups from last Tuesday's launch."
- A link to the source sheet for anyone who wants the raw numbers.
Lines invite questions ("what happened on the 12th?"). The summary answers them in advance, which is what makes the difference between a chart and a report.
Sheets → Chartcastr setup
- Build the line chart in Google Sheets, date column on the x-axis, metric column(s) on the y-axis.
- In Chartcastr add a Google Sheets source and pick the chart.
- Pick a destination (Slack, email, Google Chat).
- Set the schedule. Daily for fast-moving metrics. Weekly for noisier ones.
Range changes in the sheet are picked up automatically. If you add a new month of data, the next pulse extends the line. Full reference at the Premade Charts docs.
A common mistake
Don't truncate the y-axis to make a slope look more dramatic than it is. Sheets defaults to a sensible range for most data. The default is the right answer.
The companion chart for trends-with-context is the combo chart, useful when you want a primary metric plus a related secondary on a different scale.
