Re: [ferret_users] Masking in list command works for floats, not strings

["Riede, Hella" <hella.riede@xxxxxxx>]

Thanks, Ansley.

Usually, I first define a variable, then list it in a simple way, so that's OK as a workaround for me.

However, there doesn't seem to be a workaround for this one as all variables are defined before listing already:

can var/all
let test = {1,1,0}
let strings = {"a","b","c"}
let masked = if (test) then strings
let masked2 = xsequence(masked)
list masked2
             VARIABLE : XSEQUENCE(MASKED)
             SUBSET   : 3 points (X)
 1   / 1:  1.859-316
 2   / 2:  1.877-316
 3   / 3:  1.877-316

(Last example in mask_string.jnl, see attachment. An extra 'faulty' listing is too big / takes too long for my real dataset.)


Thanks in advance for a hint on this one.


Best wishes,
Hella






On 06/27/2017 11:35 PM, Ansley C. Manke wrote:
> Hi Hella,
> 
> Thank you for the example.  In principle, specifying an expression as 
> the argument to a command:
> 
>    yes? list if (test) then strings
> 
> should be equivalent to defining a variable with that same expression 
> and sending that to the command:
> 
>     yes? let masked = if (test) then strings
>     yes? list masked
> 
> However there winds up being a slight variation in how the computation 
> is done with occasionally different and incorrect results. (Here we're 
> seeing pointers to the strings which should be returned!)  We had a 
> similar bug report a year or two back which I think has been fixed; I'll 
> check into this.
> 
> Ansley
> 
> On 6/27/2017 9:38 AM, Riede, Hella wrote:
>> Dear ferreters,
>>
>> I discovered listing while masking seems to work. But not in all cases (see also attached script file with more examples and comments):
>>
>>
>> yes? let test = {1,1,0}
>>
>> !! problem with masked strings -> unexpected values
>> yes? let strings = {"a","b","c"}
>> yes? list if (test) then strings
>>               VARIABLE : IF (TEST) THEN STRINGS
>>               SUBSET   : 3 points (X)
>>   1   / 1:  2.109-316
>>   2   / 2:  2.109-316
>>   3   / 3:  2.109-316
>> !! repeat the listing, and the values change every time
>>
>> !! define a masked variable instead, then list - works
>> yes? let masked = if (test) then strings
>> yes? list masked
>>               VARIABLE : IF (TEST) THEN STRINGS
>>               SUBSET   : 3 points (X)
>>   1   / 1:"a"
>>   2   / 2:"b"
>>   3   / 3:""
>>
>> !! OR do the same listing for a float first
>> yes? let floats = {2,3,4}
>> yes? list if (test) then floats
>>               VARIABLE : IF (TEST) THEN FLOATS
>>               SUBSET   : 3 points (X)
>>   1   / 1:  2.000
>>   2   / 2:  3.000
>>   3   / 3:   ....
>>
>> !! now, also for strings listing while masking works
>> yes? list if (test) then strings
>>               VARIABLE : IF (TEST) THEN STRINGS
>>               SUBSET   : 3 points (X)
>>   1   / 1:"a"
>>   2   / 2:"b"
>>   3   / 3:""
>>
>>
>> In an interactive ferret session, I first had defined a masked variable for strings (in this example 'masked'), and had also listed it for testing. After that I discovered that listing while masking works too (of course I didn't know it only worked because I had defined and listed the 'masked' variable before, in the same session). So later in my ferret script I omitted defining the 'masked' variable, and used the listing while masking. The script did not crash, but gave me unexpected values like the ones above, instead of proper strings.
>>
>> Would be good to fix this, or - if the syntax of listing while masking is not supported - to catch these cases and throw an error.
>>
>> The story goes on, however, see attached script as it seems not possible to mask a string variable and then make an xsequence out of it - unless you do for instance the "faulty listing while masking" from above before the "right" listing.
>>
>>
>>
>> Best wishes,
>> Hella
>>
>> PyFerret v7.11 (beta/optim), Linux 4.4.0-72-generic - 04/19/17
> 

-- 
...............................................................................
  Hella Riede      hella.riede@xxxxxxx   +49-6131-305-4143
  Air chemistry department: Modeling & Global Observations
  Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany
  www.mpic.de   www.caribic.de
...............................................................................

!! H. Riede 06/2017
!! note, without the 'can var/all' before a new test, the behavior changes
!! as listings influence the behavior of subsequent listings


\message "problem with masked strings -> unexpected values instead of strings:"
can var/all
let test = {1,1,0}
let strings = {"a","b","c"}
list if (test) then strings
\message "(repeat the listing, and the values change every time)"


\message "works: define a masked variable instead, then list"
let masked = if (test) then strings
list masked

\message "alternatively, do the same listing for a float first"
let floats = {2,3,4}
list if (test) then floats

\message "now, also for strings listing while masking works"
list if (test) then strings



\message "the next problem comes with xsequence:"
can var/all
let test = {1,1,0}
let strings = {"a","b","c"}
let masked = if (test) then strings
list xsequence(masked)
\message "again unexpected numerical values instead of strings"


\message "but doing a 'faulty' listing first fixes it:"
can var/all
let test = {1,1,0}
let strings = {"a","b","c"}
list if (test) then strings
let masked = if (test) then strings
list xsequence(masked)


\message "NOT fixed by defining a second masked variable before:"
can var/all
let test = {1,1,0}
let strings = {"a","b","c"}
let masked = if (test) then strings
let masked2 = xsequence(masked)
list masked2