Skip to main content
cancel
Showing results for 
Search instead for 
Did you mean: 

Enhance your career with this limited time 50% discount on Fabric and Power BI exams. Ends August 31st. Request your voucher.

Reply
VizDataLtd
Helper I
Helper I

Accessing data with Stdev and Variance aggregation in place

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;
        }
    },
};

 

 

1 REPLY 1
Anonymous
Not applicable

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

Helpful resources

Announcements
July 2025 community update carousel

Fabric Community Update - July 2025

Find out what's new and trending in the Fabric community.

July PBI25 Carousel

Power BI Monthly Update - July 2025

Check out the July 2025 Power BI update to learn about new features.