Matlab Problem:

I have a set of data that has 10 columns. I have interested in creating a plot in matlab of columns 4 and 5. 4 being the x-axis and 5 being y-axis.Column 5 has some negative values which i must take out using the masking technique. I have done this. But I am not sure how to take the corresponding columns 4 value out with that so I do not get this error "Error using plot". Vectors must be the same length.