How do I make a contourf plot where the areas are supposed to be discrete (integer array instead of float)?

How do I make a contourf plot where the areas are supposed to be discrete (integer array instead of float)?

How do I make a contourf plot where the areas are supposed to be discrete (integer array instead of float)?

How do I make a contourf plot where the areas are supposed to be discrete (integer array instead of float)?

I am trying to display the tick marks inside the axis for a contourf plot.

I was trying to plot the wave1-4 of air temperature from 850hPa with contourf and it worked for wave2-4. But the picture of wave1 just showed the positive part and ignored the negative part. The data of wave1 was not wrong cause the method of fft for all wave number is the same.