How to accurately display floating point calculation results in ECharts bar charts?

Detailed explanation of ECharts histogram floating point number accuracy control

When creating bar charts with ECharts, it is crucial to display the values ​​accurately. However, the accuracy limitation of JavaScript floating-point number operation may lead to redundant numbers such as "348.900000000001" in the display result. This article provides an effective solution to the accuracy problems that arise after the sum of backend data.

Problem: JavaScript floating point precision limit

The result of backend data summation (for example, 2897.3 5451.6) is not the expected 8348.9, but 8348.90000000000001. This is not a flaw of ECharts, but an inherent precision problem in JavaScript floating-point number operations. Using such results directly for bar chart display is neither beautiful nor accurate.

Solution: Select the appropriate number of decimal places according to the data accuracy

Although the toFixed(n) method can control the number of decimal places, it cannot completely solve the accuracy problem. Too many retained digits may still have accuracy deviations, while too few retained will lose accuracy. String simulation addition operations are too complex and prone to errors.

The easiest and effective solution is: select the appropriate number of decimal places to round it according to the accuracy of the data. If the number of decimal places in the original data is only one at most (such as 2897.3 and 5451.6 in the example), retaining two decimal places can ensure a balance between accuracy and display effect.

Before passing data to ECharts, use the toFixed(2) method to process the calculation result:

 let sum = 2897.3 5451.6;
let formattedSum = sum.toFixed(2); // Keep two decimal places // ... Pass formattedSum to ECharts ...

If the original data contains more decimal places, the parameters of toFixed() method should be adjusted accordingly. For example, if the original data contains three decimal places, you can use toFixed(3) . The key is to balance accuracy and display effects based on data accuracy and display requirements.

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