Replace categorical value with numeric values

I want to replace my categorical data with numeric representation in my 4th column. They values are randomly dispersed in the column. The values are white and black. I would like to replace all "white" values with the number 1 and black with the number 0. Then I would like to export the file as ".xls" Can anyone help me? Thank you!

Answer 1

[dpb]

If categorical variable is c, then

d=double(c)-1;

presuming didn't define them except by default which will be in alphanumeric order beginning with one (1).