# Custom tooltip label with stacked chart
**URL:** https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874
**Category:** Help
**Created:** [October 2, 2024, 9:00pm UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874 "2024-10-02T21:00:35Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@mkfreeman](https://talk.observablehq.com/u/mkfreeman)
#### Post date: [October 2, 2024, 9:00pm UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/1 "2024-10-02T21:00:35Z")
In [this notebook](https://observablehq.com/d/569820eaae4023f5), I’m using an `offset: normalize` stack transform to create a stacked bar chart. I want to have a tooltip that displays the specific label “Percent: ##”, but without changing the underlying data, I can’t figure out how to customize the label.
```js
// Current approach
channels: {
customY: {
label: "Percent",
value: (d) => {
// The value of d has the data values before normalization
return d.population;
}
}
},
tip: {
// Display custom values, hide the auto generated values
format: {
customY: true,
test: (d) => d.population, // doesn't do anything
y: true,
x: true,
fill: true
}
}
```
Seems similar to [this topic](https://talk.observablehq.com/t/pointer-transforms-with-px-py-on-stacked-bar-charts/8302).
Any thoughts?
---
### Author:  [@mootari](https://talk.observablehq.com/u/mootari)
#### Post date: [October 7, 2024, 8:59am UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/2 "2024-10-07T08:59:29Z")
Hi Mike, would you mind moving this question to the [Plot discussions board](https://github.com/observablehq/plot/discussions)? Thanks!
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>
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---
### Author:  [@Fil](https://talk.observablehq.com/u/Fil)
#### Post date: [October 7, 2024, 9:47am UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/3 "2024-10-07T09:47:58Z")
I don’t think the stack offset is the correct way to think about this, because it does the two operations at the same time (i.e., it takes the original values `{y: [1, 3]}` and converts them to a normalized stack `{y1: [0, 0.25], y2: [0.25, 1]}`). The numbers you want to show as tips would be the normalized `y`: `[0.25, 0.75]`.
But you could try this:
```auto
Plot.barY(
tidy,
Plot.normalizeY("sum", {
x: "state",
y: "population",
z: "state", // the series for normalizeY
fill: "age",
sort: { color: null, x: "-y" },
offset: "normalize", // stack normalization (based on *x*)
tip: {
channels: {
population: { value: "population", label: "abs population" }
}
}
})
).plot({ y: { percent: true } })
```
---
### Author:  [@mkfreeman](https://talk.observablehq.com/u/mkfreeman)
#### Post date: [October 7, 2024, 2:01pm UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/4 "2024-10-07T14:01:21Z")
Thanks @Fil! That’s close, but it is showing a custom label next to the absolute value. Is there a way to change the label next to the percentage label (not the total, but the percentage?). I was able to get it by just changing the data, which wasn’t too bad:
```js
Plot.tip(
tidy.map((d) => {
d.percent = d.population;
return d;
}),
{
...Plot.pointer(
Plot.stackY({
x: "state",
y: "percent",
fill: "age",
sort: { color: null, x: "-y" },
offset: "normalize"
})
)
}
)
```
(@mootari I’ll post future questions to the GitHub board)
---
### Author:  [@mbostock](https://talk.observablehq.com/u/mbostock)
#### Post date: [October 7, 2024, 2:11pm UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/5 "2024-10-07T14:11:11Z")
Please move this discussion to GitHub. Thank you!
---
### Author:  [@mbostock](https://talk.observablehq.com/u/mbostock)
#### Post date: [October 7, 2024, 2:11pm UTC](https://talk.observablehq.com/t/custom-tooltip-label-with-stacked-chart/9874/6 "2024-10-07T14:11:20Z")