@acer Thanks. I have implemented the same thing as suggested by @Kitonum also. It worked.
Actually I was solving system of DE's for different values of some parameters say p and q, and storing the result obtained from dsolve command at zero in a matrix. Then I tried to plot (p,q,z), it was taking 1 to 21 by default, but the parameters I varied are from 0 to 0.6. Then I used tickmarks in the code, by mapping (1..11) on to (0..0.5) using linear equation, then I got the required one. Thanks for the suggestion.
ll1 := 0.; ul1 := 0.6; ll2 := 0.; ul2 := 0.6; h1 := (ul1 - ll1)/20.0; h2 := (ul2 - ll2)/20.0;
ax1 := 1.0; ax2 := 21.0; bx1 := ll1; bx2 := ul1; intrcptx := bx1 - (bx2 - bx1)*ax1/(ax2 - ax1); slpx := (bx2 - bx1)/(ax2 - ax1);
ay1 := 1.0; ay2 := 21.0; by1 := ll2; by2 := ul2; intrcpty := by1 - (by2 - by1)*ay1/(ay2 - ay1); slpy := (by2 - by1)/(ay2 - ay1);
Then I used
tickmarks = [[seq(i = i*slpx + intrcptx, i = ax1 .. ax2, 5)], [seq(i = i*slpy + intrcpty, i = ay1 .. ay2 - 1, 5)], default]
in matrixplot(). It worked