Array Size must be greater than one

Hi All,

I have create a new crystal report in which the data are loaded into group based on one variable from Database table and I need to calculate the stddev in group wise so I used the below things.

1. Feed the data of one column from group to array and fien the stddev for it.
2. will reset the array for each group based on the below formula.

and my issue is while im trying to supply only one value for the group then it returning the error below.

Reset Formula:

WhilePrintingRecords;

NumberVar array arr := 0;

Numbervar x := 0;

Numbervar i := 0;

Stddev:

WhilePrintingRecords;

NumberVar array arr;

StdDev (arr);

Please help me on this.