contour with logarithmic axis

[Hilmar GUDMUNDSSON GL D21 2-4093 <hilmar(at)vaw.baug.ethz.ch>]

I'm having problems with contour using a logarithmic x axis.  When
I contour the data using

      CONTOUR, matrix, x,y, xrange = [xmin, xmax], yrange = [ymin,
ymax], $
        xtitle = x_t, ytitle = y_t,  max_value = 1000., level = levels,
xtype=1

the contour lines only appear on a part of the plot. Depending on the
exact values of xmin and xmax, the fraction of the plotting area that is
contoured changes in an erratic fashion. I can used alog10(matrix) and
alog10(x),  which produces a plot which is OK but I would rather like to
stick to having the x axis logarithmic if possible.

Has someone else run into this problem? Any solutions?

hilmar