# Re: white space at the edge of colored contour plot

Hi Sang-ki,

The FILL command is an interpolation operation (it has to find a contour path between grid cells).  The SHADE command is not (it simply treats each cell independently).  Normally Ferret makes a small adjustment in the extent of  the plotting region to accomodate the 1/2 grid cell variation that exists between these two methods of rendering the graphics.

To see this difference look at the X axis limits used by the PLOT+ engine ("ppl list xaxis") in this output:

yes? ppl list xaxis
XAXIS QUALITIES
LO= 1.30E+02 HI= 2.80E+02 TIC= 2.00E+01 LEN= 8.00E+00
yes? fill/x=130e:80w/y=20s:20n/l=1 sst
yes? ppl list xaxis
XAXIS QUALITIES
LO= 1.31E+02 HI= 2.79E+02 TIC= 2.00E+01 LEN= 8.00E+00
From what you've described I presume that you are using /OVERLAY or /HLIMITS and thereby (accidentally?) taking control of the extent of the plotting region.  The following command illustrates how you can create white space at the edges this way:

yes? fill/x=130e:80w/y=20s:20n/l=1/hlimits=130e:80w sst

Solution: As long as you set the data region ("x=130e:80w" above) to be at least a grid cell larger on each side than the plotting region ("hlimits=130e:80w" above) you can avoid this problem.

- steve

============================

Ansley Manke wrote:

Hi Sang-ki
Yes, we've seen this.  Isyour data on an irregularly spaced
grid? Depending on the data and the grid it's on, the algorithm
that does the fill plot can't always fill the entire region.  A
workaround is to do a SHADE plot and then overlay it with
your FILL command, using the same contour levels.

Ansley

Sang-ki Lee wrote:

> Hi. My problem is that when "fill" command is used for colored contour,
> sometimes I get white space at top or side edge of the colored contour
> plot. This problem come and go, and it is nothing to do with missing
> data point. Has anyone noticed this problem?
>
> I am using v5.60 on Linux.
>
> Thank you.
>
> Sang-ki

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