Re: [ferret_users] Masking and set var/bad = 0

["Ansley C. Manke" <ansley.b.manke@xxxxxxxx>]

Hi Josh,

Zero is a bit problematic for use as a bad-value, especially when your data contains zeros. Try it this way:

LET no_strat = if stratified[l=1:12@sum] eq 0 then 1

You don't need an "else" here. By default in an IF, if there is no else it's treated as "else missing". As I've written that command, the default missing-value of -1.e34 will be used for missing-data. If you want to assign a particular missing-value, then you can do that right on the LET command.

LET/bad=-9999 no_strat = if stratified[l=1:12@sum] eq 0 then 1

Also have a look in the documentation about the distinction between IF and IFV. There can be valid values of 0 in data. Here's a variable with one value that's 0 and another that's missing.

yes? let var = {6, 2, 0, 2, , 3}

yes? list IF var then 1
VARIABLE : IF VAR THEN 1
SUBSET : 6 points (X)
1 / 1: 1.000
2 / 2: 1.000
3 / 3: ....
4 / 4: 1.000
5 / 5: ....
6 / 6: 1.000

yes? list IFV var then 1
VARIABLE : IFV VAR THEN 1
SUBSET : 6 points (X)
1 / 1: 1.000
2 / 2: 1.000
3 / 3: 1.000
4 / 4: 1.000
5 / 5: ....
6 / 6: 1.000

By the way, you shouldn't be able to X as a variable name. (Did Ferret really let you use that command? Or were you just simplifying for writing the question? A command with LET X = should return an error, " **ERROR: command syntax: cannot define: X") X is a reserved keyword , used to refer to the x coordinate of the grid, so it's best to use other variable names.

On 6/21/2019 8:40 AM, JoshAB1995@xxxxxxxxxxx wrote:

Good Afternoon,

I’m having an issue using the set var/bad = 0 dataset command. I’ve defined some new regions as the following, to indicate presence or absence of stratification:

let X = if stratified[l=1:12@sum] eq 0 then 1 else 0

let Y = if stratified[l=10:2@sum] eq 0 and stratified[l=3:9@sum] gt 0 and stratified[l=3:9@sum] le 3 then 1 else 0

So this creates a map of 1’s where the region matches what is described in the mask, and 0’s where it doesn’t.

So now I try to mask out all of the 0’s so that I can create shapefiles of the areas matching my description using:

Set var/bad = 0 X

Set var/bad = 0 Y

However, this seems to mask the entirety of my data and I get a screen telling me that no data is available.

Does anyone have any clues as to why this happens? Because I am lost for ideas, I think it might be to do with the fact that both of these ‘original’ datasets will have values of 0 (as seen in original definitions), and so it is masking the original dataset, does anyone know how I can make the mask apply only to my map of 1’s and 0’s?

Many thanks,

Josh

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--
Ansley Manke
NOAA/PMEL Science Data Integration Group
7600 Sand Point Way NE
206-526-6246