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Re: mask values in NetCDF file

The easiest way to do this is in Ferret itself. There are a lot of ways you could do this with defining new variables, etc., but you could also just plot the normal variable and then fill in for the special value. E.g., to overlay a grey special value mask over a normal temperature mask:

shade/lev=(0,100,10) temp
shade/over/pal=grey/lev=(-99.9)/nolab temp

This might not be exactly right as I haven't tested it.

You might be able to automate this somewhat in NetCDF. I can't remember if Ferret allows you to directly read variable attributes from a NetCDF file (I think it does, but I can't remember how). Then you would define a new variable attribute that would contain this special value and then just read the value in ferret - this way if the special value is different for different data files or variables you don't have to hard code it in a .JNL file.

Even if ferret doesn't let you do this then you might be able to define a variable on a 0-D (scalar) grid and test against that.


On Wednesday, January 16, 2002, at 12:27 PM, Yunyao Qu wrote:

Dear All,
We know how to specify the Missing Values in NetCDF file(using Missing
Flag) and draw it in expected  color(e.g., black, gray..).
But I have another kind of values in NetCDF(in addition to missing
values) which I  need to mask (draw it in a controllable color, because
these values are not the normal valid measurement values and also we do
not want to describe them as Missing values).
How can we define them in NetCDF and draw it in a desired color?

Yunyao "Frank" Qu
Satellite Active Archive (SAA)

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