Error using boxplot>straightenX

Hi guys and thanks in advance. I have been trying to create boxplot for a matrix that is created after the result of series of computation. However when I do the boxplot command:

boxplot (x)
%The following error come up
Error using boxplot>straightenX (line 893)
'X' parameter must be a numeric vector or matrix.
Error in boxplot (line 273)
[xDat,gDat,origRow,xlen,gexplicit,origInd,origNumXCols] = straightenX(x,g);

I thought maybe if I rounded the value within the matrix it will be solved but when I do:

round(x,2)
%The following error came up
Error using sym/round
Too many input arguments.

So what is a good solution for this error in odrer to be able to get the boxplot for my matrix?