Matlab contourf colorbar help

[garpar78]

Hi,
I am using contourf to plot antenna near-field patterns in dB, and I am trying to force the colorbar to start at 0 (my values are normalized, so they are -'ve dB). The highest value I have is about -2dB, but I want the colorbar to start at 0 dB, not -2 dB.
Any ideas? (hopefully I'm just missing the obvious)

 

[JacobL]

you have data<0 but want the plot to start from 0?
what do you want the negative values to be? truncated?
you can just offset the data to a temporary matrix and plot it, and it might be easier this way.