plotting each column of an array with first column

[Alex22]

Hi,
I have a 1000*200 matrix that is put in a (QString **) type variable (str). Data is get in this str by reading a binary file. I need to plot each column of str with first column (first column is horizontal axe and selected column is vertical axe) but it must be cast to float. Please help me for plotting this.

[Alex22]

thanks a lot if a person give me some help!!!