Re: [ferret_users] Generating zero-filled strings - for use in file-naming perhaps ( for example 25 -> "025" or "0025")

[Andrew Wittenberg <Andrew.Wittenberg@xxxxxxxx>]

Mick,

There's a simpler way -- use the zw ("zero-filled width") keyword inside 
your backquoted (``) immediate mode expression:

   repeat/k=1:121 (go ptest; frame/file="image_`k,zw=3`.gif" )

This feature was introduced in Ferret version 5.4.  It is documented here:

http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/EMBEDDED-XPRESSIONS#_VPINDEXENTRY_563

Andrew


On Tue, 30 Nov 2010, mick spillane wrote:

> Quick Demo:  Cut and paste this in Ferret
>       repeat/k=8:11 list/nohead substring("`k+10^3`",2,3)
> --------------------------------------------------
> Hello All,
>    A situation that comes up fairly often for me is creating, within Ferret, 
> a set of filenames for I/O, for example "image_001.gif" ... "image_121.gif" 
> in creating the frames of an animation.
>
> In this case a "clunky" solution would be
>    repeat/k=1:9         ( go ptest ; frame/file="image_00"`k`".gif ")
>    repeat/k=10:99     ( go ptest ; frame/file="image_0"`k`".gif" )
>    repeat/k=100:121 ( go ptest ; frame/file="image_"`k`".gif" )
> where "go ptest" just generates a sample plot on the screen.
>
> While it's not rocket science, and has probably been used by others, it just 
> struck me that the "substring" function is well-suited to this task (there 
> may be other simple(r) methods for which the appropriate 2x4 has not yet 
> impinged on my cranium).
>
> The 3-digit "001" ... "121" can be generated by adding 1000=10^3 and lopping 
> off the leading "1", as in
>    repeat/k=1:121 list/nohead substring("`k+10^3`",2,3)
> Here the 2 never changes - it just says "start with the 2nd character". The 
> 3's specify the number of characters in the strings produced.
>
> So to achieve the same result as the "clunky" three step frame naming above, 
> one could write
>    repeat/k=1:121  ( let id="image_"+substring("`k+10^3`",2,3)+".gif" ; go 
> ptest ; frame/file=`id` )
>
> Hope this is of use to others, (and is not already in the user group 
> archives)
>    Mick