Accessing data with Stdev and Variance aggregation in place

VizDataLtd — Wed, 22 May 2024 14:16:07 GMT

Hello,

The user is able to select an aggregation type in the frontend by clicking the down arrow on a number series (e.g. Sum, Min, Max, Count). I have identified that which method they pick is stored within expr.func (I hope this helps someone; it took me a while to find it). I built the following mapping to let me apply the correct calculation based on expr.func. But it won't work for stdev or variance. After some hunting, I realise that when Stdev or Variance is selected by the user, the values passed into options.dataViews[0].categorical.values[numberIndex].values are all zeroes (e.g. [0,0,0,0]). I would expect this if the numbers are identical, but they are not.

To put it another way, the following log console.log(options.dataViews[0].categorical.values[numberIndex].values); outputs [3000, 2000, 1000, 5000] if I have Sum selected, but [0,0,0,0] if I have Stdev selected. Is Stdev/variance not supported for custom visuals or is there some kind of rounding issue going on - and if so how do i fix it please?

export const AGGREGATION_METHODS = { 0: { name: 'sum', calculate: (values: number[]) => values.reduce((a, b) => a + b, 0) }, 1: { name: 'avg', calculate: (values: number[]) => values.reduce((a, b) => a + b, 0) / values.length }, 2: { name: 'count distinct', calculate: (values: number[]) => new Set(values).size }, 3: { name: 'min', calculate: (values: number[]) => Math.min(...values) }, 4: { name: 'max', calculate: (values: number[]) => Math.max(...values) }, 5: { name: 'count', calculate: (values: number[]) => values.length }, 6: { name: 'median', calculate: (values: number[]) => { const sorted = values.slice().sort((a, b) => a - b); const mid = Math.floor(sorted.length / 2); return sorted.length % 2 !== 0 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2; } }, 7: { name: 'stdev', calculate: (values: number[]) => { const mean = values.reduce((sum, v) => sum + v, 0) / values.length; const variance = values.reduce((sum, v) => sum + Math.pow(v - mean, 2), 0) / (values.length - 1); return Math.sqrt(variance); } }, 8: { name: 'variance', calculate: (values: number[]) => { const mean = values.reduce((a, b) => a + b, 0) / values.length; return values.reduce((a, b) => a + Math.pow(b - mean, 2), 0) / values.length; } }, };

Re: Accessing data with Stdev and Variance aggregation in place

Anonymous — Thu, 23 May 2024 10:04:34 GMT

Hi @VizDataLtd ,

May I confirm if your question pertains to Power BI? If so, could you kindly provide some data or screenshots to help me better understand the problem? Thank you.

Best Regards

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Accessing data with Stdev and Variance aggregation in place

Re: Accessing data with Stdev and Variance aggregation in place