| turn a string value into variable name [message #63041] |
Thu, 23 October 2008 15:30  |
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Nick[2]
Messages: 2
Registered: October 2008
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Junior Member |
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Hello,
I am restoring over 100 .sav files and creating structures for
analysis. Each .sav represents a differenct scenario and ideally I
would like to name the created structure in sequential format (case1,
case2...casen).
To pull the data in I am using a for loop (all .sav have identical
array names) and I'd like to use the counter to name the variable. Is
it possible to turn a string into a variable name?
Thanks,
Nick
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| Re: turn a string value into variable name [message #63122 is a reply to message #63041] |
Wed, 29 October 2008 08:09  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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loebasboy writes:
> To know if my code is good coding I'll explain myself why I want to
> use this type of coding.
>
> I want to write function to read data out of a HDF5 file with a
> certain structure. The HDF5 file consists of a digital aerial image
> with callibration information per band and such. What I wanted to do
> is that I want to read in the central wavelength of a band, analyse it
> and define the name of that band so that I can write the data of the
> band in a variable with the right name of that band. Lets say that the
> central wavelength of this band is 752 nm, I would like to write the
> information of this band in the variable "NIR". So I first read in the
> central wavelength of a certain band, compare it with a reference
> value (depends on the sensor), and then write the information of the
> band in the right named variable. In this way I could do analyses with
> logical named variables...for instance, the calculation of the NDVI
> simply becomes (NIR-R)/(NIR+R) in the code.
Well, I think I'll just stand behind my statement. :-)
Cheers,
David
P.S. Wouldn't just using simple variables make your program easier
to understand!? That's sort of the purpose of variables, to
stand in for the real thing.
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: turn a string value into variable name [message #63125 is a reply to message #63041] |
Wed, 29 October 2008 07:55 |
loebasboy
Messages: 26
Registered: August 2008
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Junior Member |
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On 29 okt, 14:34, David Fanning <n...@dfanning.com> wrote:
> loebasboy writes:
>> On 23 okt, 23:56, David Fanning <n...@dfanning.com> wrote:
>>> Nick writes:
>>>> I am restoring over 100 .sav files and creating structures for
>>>> analysis. =A0Each .sav represents a differenct scenario and ideally I
>>>> would like to name the created structure in sequential format (case1,
>>>> case2...casen).
>
>>>> To pull the data in I am using a for loop (all .sav have identical
>>>> array names) and I'd like to use the counter to name the variable. =A0I=
>> s
>>>> it possible to turn a string into a variable name?
>
>>> The EXECUTE command can do this:
>
>> Thank you David, I had the same question !
>
> I'm glad the answer is helpful, but I would say in general
> that 9 people out of 10 who are writing code like this
> are *probably* doing the wrong thing. That is to say,
> the good reasons for creating variables on the fly,
> inside a procedure, are few and far between. I'd look
> pretty hard for alternatives before I ever coded something
> like this up.
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -
To know if my code is good coding I'll explain myself why I want to
use this type of coding.
I want to write function to read data out of a HDF5 file with a
certain structure. The HDF5 file consists of a digital aerial image
with callibration information per band and such. What I wanted to do
is that I want to read in the central wavelength of a band, analyse it
and define the name of that band so that I can write the data of the
band in a variable with the right name of that band. Lets say that the
central wavelength of this band is 752 nm, I would like to write the
information of this band in the variable "NIR". So I first read in the
central wavelength of a certain band, compare it with a reference
value (depends on the sensor), and then write the information of the
band in the right named variable. In this way I could do analyses with
logical named variables...for instance, the calculation of the NDVI
simply becomes (NIR-R)/(NIR+R) in the code.
The code:
FOR m = 0, nr_bands[0]-1 DO BEGIN
ctrlwav_str = string("/SensorData/Band",string(m+1,
format='(I03)'),"/SpectralResponse/CentralWavelength")
dataset_id = H5D_OPEN(file_id, ctrlwav_str)
ctrlwav[m] = H5D_READ(dataset_id)
H5D_CLOSE, dataset_id
IF (abs(ctrlwav[m] - color_id[0]) LT 0.015) THEN
col_band[m] = "PAN"
IF (abs(ctrlwav[m] - color_id[1]) LT 0.015) THEN
col_band[m] = "B"
IF (abs(ctrlwav[m] - color_id[2]) LT 0.015) THEN
col_band[m] = "G"
IF (abs(ctrlwav[m] - color_id[3]) LT 0.015) THEN
col_band[m] = "R"
IF (abs(ctrlwav[m] - color_id[4]) LT 0.015) THEN
col_band[m] = "NIR"
data_str = string("/SensorData/Band",string(m+1,
format='(I03)'),"/SensorData")
dataset_id = H5D_OPEN(file_id, data_str)
tmp = Execute(col_band[m] + ' = H5D_READ(dataset_id)')
H5D_CLOSE, dataset_id
ENDFOR
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| Re: turn a string value into variable name [message #63141 is a reply to message #63041] |
Wed, 29 October 2008 06:34 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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loebasboy writes:
> On 23 okt, 23:56, David Fanning <n...@dfanning.com> wrote:
>> Nick writes:
>>> I am restoring over 100 .sav files and creating structures for
>>> analysis. =A0Each .sav represents a differenct scenario and ideally I
>>> would like to name the created structure in sequential format (case1,
>>> case2...casen).
>>
>>> To pull the data in I am using a for loop (all .sav have identical
>>> array names) and I'd like to use the counter to name the variable. =A0I=
> s
>>> it possible to turn a string into a variable name?
>>
>> The EXECUTE command can do this:
>
> Thank you David, I had the same question !
I'm glad the answer is helpful, but I would say in general
that 9 people out of 10 who are writing code like this
are *probably* doing the wrong thing. That is to say,
the good reasons for creating variables on the fly,
inside a procedure, are few and far between. I'd look
pretty hard for alternatives before I ever coded something
like this up.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: turn a string value into variable name [message #63269 is a reply to message #63041] |
Wed, 29 October 2008 08:30 |
Vince Hradil
Messages: 574
Registered: December 1999
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Senior Member |
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On Oct 29, 10:29 am, loebasboy <stijn....@gmail.com> wrote:
> On 29 okt, 16:09, David Fanning <n...@dfanning.com> wrote:
>
>
>
>> loebasboy writes:
>>> To know if my code is good coding I'll explain myself why I want to
>>> use this type of coding.
>
>>> I want to write function to read data out of a HDF5 file with a
>>> certain structure. The HDF5 file consists of a digital aerial image
>>> with callibration information per band and such. What I wanted to do
>>> is that I want to read in the central wavelength of a band, analyse it
>>> and define the name of that band so that I can write the data of the
>>> band in a variable with the right name of that band. Lets say that the
>>> central wavelength of this band is 752 nm, I would like to write the
>>> information of this band in the variable "NIR". So I first read in the
>>> central wavelength of a certain band, compare it with a reference
>>> value (depends on the sensor), and then write the information of the
>>> band in the right named variable. In this way I could do analyses with
>>> logical named variables...for instance, the calculation of the NDVI
>>> simply becomes (NIR-R)/(NIR+R) in the code.
>
>> Well, I think I'll just stand behind my statement. :-)
>
>> Cheers,
>
>> David
>
>> P.S. Wouldn't just using simple variables make your program easier
>> to understand!? That's sort of the purpose of variables, to
>> stand in for the real thing.
>
>> --
>> David Fanning, Ph.D.
>> Fanning Software Consulting, Inc.
>> Coyote's Guide to IDL Programming:http://www.dfanning.com/
>> Sepore ma de ni thui. ("Perhaps thou speakest truth.")- Tekst uit oorspronkelijk bericht niet weergeven -
>
>> - Tekst uit oorspronkelijk bericht weergeven -
>
> simple AND logical named variables? ;)
http://en.wikipedia.org/wiki/Obfuscated
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| Re: turn a string value into variable name [message #63270 is a reply to message #63122] |
Wed, 29 October 2008 08:29 |
loebasboy
Messages: 26
Registered: August 2008
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Junior Member |
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On 29 okt, 16:09, David Fanning <n...@dfanning.com> wrote:
> loebasboy writes:
>> To know if my code is good coding I'll explain myself why I want to
>> use this type of coding.
>
>> I want to write function to read data out of a HDF5 file with a
>> certain structure. The HDF5 file consists of a digital aerial image
>> with callibration information per band and such. What I wanted to do
>> is that I want to read in the central wavelength of a band, analyse it
>> and define the name of that band so that I can write the data of the
>> band in a variable with the right name of that band. Lets say that the
>> central wavelength of this band is 752 nm, I would like to write the
>> information of this band in the variable "NIR". So I first read in the
>> central wavelength of a certain band, compare it with a reference
>> value (depends on the sensor), and then write the information of the
>> band in the right named variable. In this way I could do analyses with
>> logical named variables...for instance, the calculation of the NDVI
>> simply becomes (NIR-R)/(NIR+R) in the code.
>
> Well, I think I'll just stand behind my statement. :-)
>
> Cheers,
>
> David
>
> P.S. Wouldn't just using simple variables make your program easier
> to understand!? That's sort of the purpose of variables, to
> stand in for the real thing.
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")- Tekst uit oorspronkelijk bericht niet weergeven -
>
> - Tekst uit oorspronkelijk bericht weergeven -
simple AND logical named variables? ;)
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| Re: turn a string value into variable name [message #94471 is a reply to message #63122] |
Thu, 01 June 2017 15:48 |
laura.hike
Messages: 87
Registered: September 2013
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Member |
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So now I want to do this in order to use a loop to add lines to a plot and then make a legend. I need the plot names to all be different so I can use them in the "target" argument, but I can otherwise make the plot commands identical, e.g.,
p1 = plot(xbin, pdf, color = linecolors[nsea], thick = 2, name = seanames[nsea], /overplot)
Based on David's comment, I tried
execute('p5 = plot(xbin, pdf, color = linecolors[nsea-1], thick = 2, name = seanames[nsea-1], /overplot)')
but this didn't do anything except return a "1". I'm really not excited about putting in a plot command (with an 'if' statement' for each of the lines I want to overplot.
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| Re: turn a string value into variable name [message #94472 is a reply to message #94471] |
Fri, 02 June 2017 02:59 |
Markus Schmassmann
Messages: 129
Registered: April 2016
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Senior Member |
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On 06/02/2017 12:48 AM, laura.hike@gmail.com wrote:
> So now I want to do this in order to use a loop to add lines to a plot and then make a legend. I need the plot names to all be different so I can use them in the "target" argument, but I can otherwise make the plot commands identical, e.g.,
>
> p1 = plot(xbin, pdf, color = linecolors[nsea], thick = 2, name = seanames[nsea], /overplot)
>
> Based on David's comment, I tried
>
> execute('p5 = plot(xbin, pdf, color = linecolors[nsea-1], thick = 2, name = seanames[nsea-1], /overplot)')
>
> but this didn't do anything except return a "1". I'm really not excited about putting in a plot command (with an 'if' statement' for each of the lines I want to overplot.
I don't see why you'd use an EXECUTE here, try the code below
pp=objarr(n_lines)
for nsea=0,n_lines-1 do if <condition> then pp[nsea]=plot( xbin, pdf, $
color = linecolors[nsea-1], thick = 2, name = seanames[nsea-1], $
/overplot )
l=legend(target=pp)
If this doesn't help, please explain in more detail what you want to do,
it's now fully clear from your post.
Good Luck, Markus
PS: The main topic of this thread is mostly obsolete as of IDL 8.0 with
the introduction of HASH
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