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Re: [ferret_users] Difference between fill and shade



Hi

On Mon, May 25, 2020 at 4:44 PM Olivier Marti <olivier.marti@xxxxxxxxxxxx> wrote:
SHADE draws squares (or rectangles) of uniforms colours. It use the grid boundaries to draw the squares. If the boundaries are not present in the input file, it will compute the boundaries by taking the middle of the grid points. The 'pixels' that you observe are just the grid of the data.

FILL draws a continuous field by interpolating the data between two grid points. The plot does not appears as pixelated. But be aware that interpolation algorithm used by FILL adds some information between grid points that are not present in the actual data.

The following demonstration might be fun:

! copy and paste these commands
define axis/x=1:3:2/units=degrees_east xax
define axis/y=1:3:2/units=degrees_north yax
let var = x[gx=xax] + 2 * y[gy=yax]
set mode grat:dash
fill/hlimits=0:4:2/vlimits=0:4:2/lev=(-Inf)(2)(4)(6)(8)(Inf) var
shade/hlimits=0:4:2/vlimits=0:4:2/lev=(-Inf)(2)(4)(6)(8)(Inf) var


Observe how FILL interpolates values between gridpoints.

Ryo


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