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| 1 | +--- |
| 2 | +title: How to format the percent in a label for a pie or donut chart |
| 3 | +description: How to format the percent in a label for a pie or donut chart |
| 4 | +type: how-to |
| 5 | +page_title: How to format the percent in a label for a pie or donut chart |
| 6 | +slug: chart-format-percent |
| 7 | +position: |
| 8 | +tags: |
| 9 | +ticketid: 1419362 |
| 10 | +res_type: kb |
| 11 | +--- |
| 12 | + |
| 13 | +## Environment |
| 14 | +<table> |
| 15 | + <tbody> |
| 16 | + <tr> |
| 17 | + <td>Product</td> |
| 18 | + <td>Charts for Blazor</td> |
| 19 | + </tr> |
| 20 | + </tbody> |
| 21 | +</table> |
| 22 | + |
| 23 | + |
| 24 | +## Description |
| 25 | +When you use templates to customize the appearance of the labels, you may need to implement some application logic there or to implement complex formatting of the numbers. |
| 26 | + |
| 27 | +This article shows how to format the percent in a label for a pie or donut chart to have a desired number of decimals and to be a number between 0 and 100, instead of the default number between 0 and 1 that has many decimal places: |
| 28 | + |
| 29 | + |
| 30 | + |
| 31 | +## Solution |
| 32 | +To customize the percentage display, you need to |
| 33 | + |
| 34 | +1. Use a custom [template]({%slug components/chart/label-template-format%}#templates) to show the `percentage` field. |
| 35 | + |
| 36 | +2. Implement the desired rounding/formatting function in a JavaScript file (in the example below, we will call it `template-helpers.js` and it resides in the `wwwroot` folder). |
| 37 | + |
| 38 | +3. Reference that file in your root component (`_Host.cshtml` for a server-side app, or `index.html` for a client-side app). |
| 39 | + |
| 40 | +4. Call the custom formatting function from the template and pass the needed arguments to it. It must return the string you want shown in the template. |
| 41 | + |
| 42 | +````Razor |
| 43 | +@using Telerik.Blazor |
| 44 | +@using Telerik.Blazor.Components.Chart |
| 45 | +
|
| 46 | +<TelerikChart> |
| 47 | + <TelerikChartSeriesItems> |
| 48 | + <TelerikChartSeries Type="ChartSeriesType.Pie" Data="@pieData" |
| 49 | + Field="@nameof(MyPieChartModel.SegmentValue)" CategoryField="@nameof(MyPieChartModel.SegmentName)"> |
| 50 | + <TelerikChartSeriesLabels Visible="true" Template="@segmentTemplate"></TelerikChartSeriesLabels> |
| 51 | + </TelerikChartSeries> |
| 52 | + </TelerikChartSeriesItems> |
| 53 | +
|
| 54 | + <TelerikChartTitle Text="Revenue per product"></TelerikChartTitle> |
| 55 | +
|
| 56 | + <TelerikChartLegend Position="ChartLegendPosition.Right"> |
| 57 | + </TelerikChartLegend> |
| 58 | +</TelerikChart> |
| 59 | +
|
| 60 | +@code { |
| 61 | + //this is where we call our custom rounding function |
| 62 | + string segmentTemplate = "#=value#\n#= round(percentage * 100, 1)#%"; |
| 63 | +
|
| 64 | + //below is just some data to feed the display |
| 65 | + public class MyPieChartModel |
| 66 | + { |
| 67 | + public string SegmentName { get; set; } |
| 68 | + public double SegmentValue { get; set; } |
| 69 | + } |
| 70 | +
|
| 71 | + public List<MyPieChartModel> |
| 72 | + pieData = new List<MyPieChartModel> { |
| 73 | + new MyPieChartModel { |
| 74 | + SegmentName = "Product 1", |
| 75 | + SegmentValue = 1 |
| 76 | + }, |
| 77 | + new MyPieChartModel { |
| 78 | + SegmentName = "Product 2", |
| 79 | + SegmentValue = 3 |
| 80 | + }, |
| 81 | + new MyPieChartModel { |
| 82 | + SegmentName = "Product 3", |
| 83 | + SegmentValue = 5 |
| 84 | + } |
| 85 | + }; |
| 86 | +} |
| 87 | +```` |
| 88 | +````JavaScript |
| 89 | +//From https://www.jacklmoore.com/notes/rounding-in-javascript/ |
| 90 | +function round(value, decimals) { |
| 91 | + return Number(Math.round(value + 'e' + decimals) + 'e-' + decimals); |
| 92 | +} |
| 93 | +```` |
| 94 | +````Index |
| 95 | +<head> |
| 96 | + <!-- there may be other content here --> |
| 97 | + |
| 98 | + <script src="~/template-helpers.js"></script> |
| 99 | + |
| 100 | + <!-- there may be other content here --> |
| 101 | +</head> |
| 102 | +```` |
| 103 | + |
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