Re: [ferret_users] accessing statistics symbols in if/then statements

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

Hi
Russ has a solution if you want the length of the axis.  If you want the 
number of valid points in a variable, you could use the @NGD 
transformation instead of `return=Lsize`.

  let n_ok = p[x=@ngd,y=@ngd,z=@ngd,t=@ngd]

I'd like to just explain more about what you ran into here:

The command parser evaluates symbols ($symbol_name) as the command is 
read in, and substitutes those symbols. The commands aren't executed at 
that time; we are just getting the full command line with any symbols or 
grave-accent expressions evaluated. When you put a set of commands 
together with the semicolon, they are parsed as a single command, 
substituting symbols and grave-accent expressions and then after that, 
the long input line broken up into separate commands and then finally 
they are executed.  Until the STAT command is executed the value of 
STAT_NGOOD doesn't exist.

A solution for that is to do the IF statements as a block if within your 
script.  This should work fine:

let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
if `6 LT 10` then
  statistics p
  let pnum = ($stat_ngood))
endif






On 9/24/2012 11:29 PM, Jennifer.Abernethy@xxxxxxxx wrote:
> Hi,
>
> I'm running into a problem accessing the symbol $STAT_NGOOD when I use the statistics command in an if/then statement. It all works great when not used in an if/then statement.
> Can anyone help me make sense of this?
>
>
> This works great:
>
> let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
> statistics p
> let pnum = ($stat_ngood)
>
> yes? go try_statstest.jnl
> let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
> statistics p
>   
>               PSL[D=spsl_soi,T="16-jan-2000":"16-jan-2010"]
>               LONGITUDE: 0E
>               LATITUDE: 0
>               Z:  N/A
>               TIME: 15-JAN-2000 12:00 to 14-JAN-2010 00:00
>               DATA SET: N/A
>   
>   Total # of data points: 120 (1*1*1*120)
>   # flagged as bad  data: 0
>   Minimum value: -2.2286
>   Maximum value: 3.9071
>   Mean    value: -0.13333 (unweighted average)
>   Standard deviation: 1.0054
> let pnum = ($stat_ngood)
>   !-> DEFINE VARIABLE pnum = 120
>
>
>
> But then I put it in a if/then statement.  Stat_ngood exists, but I can't save it:
>
> let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
> if `6 LT 10` then (statistics p; show sym stat*;  let pnum = ($stat_ngood)) endif
>
> yes? go try_statstest.jnl
> let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
> if `6 LT 10` then  (statistics p ; let pnum = ($stat_ngood))  endif
>   !-> if 1 then  (statistics p ; let pnum =  )  endif
>   
>               PSL[D=spsl_soi,T="16-jan-2000":"16-jan-2010"]
>               LONGITUDE: 0E
>               LATITUDE: 0
>               Z:  N/A
>               TIME: 15-JAN-2000 12:00 to 14-JAN-2010 00:00
>               DATA SET: N/A
>   
>   Total # of data points: 120 (1*1*1*120)
>   # flagged as bad  data: 0
>   Minimum value: -2.2286
>   Maximum value: 3.9071
>   Mean    value: -0.13333 (unweighted average)
>   Standard deviation: 1.0054
> STAT_MIN = "-2.2286"
> STAT_MAX = "3.9071"
> STAT_MEAN = "-0.13333"
> STAT_STD = "1.0054"
> STAT_NGOOD = "120"
> STAT_NBAD = "0"
>   **ERROR: command syntax: PNUM = ???
> DEFINE VARIABLE pnum =
> Command file, command group, or REPEAT execution aborted
>
>
> but it's fine again if I move the statistics command out of the if/then stmt:
>
> !works
> let p =  psl[d=1,t="16-jan-2000":"16-jan-2010"]
> statistics p
> if `6 LT 10` then (let pnum = ($stat_ngood)) endif
>
>
>
> I need to have the statistics run in an if/then statement, because my real if test is if the year actually exists in the file (i.e. if it doesn't, can't run stats on it to begin with).
>
> However, the reason I'm using `statistics` is that I need to get the length of p (on the L axis) - any other ways to do this?
>
> Is there also any command that clears all data and symbols, axes, etc in ferret? I see cancel data,symbols etc but it looks like you have to do a bunch of cancel commands, clearing each thing one by one - anything that does it all in one command?
>
> thanks,
> jenny