[gradsusr] Contingency Table

[Amulya Chevuturi]

Dear Eric,

Thank you so much for the help. The explanation of the subtle difference
between data variable and script variable was excellent.

Warm regards,

Amulya Chevuturi
School of Environmental Sciences
Jawaharlal Nehru University
New Delhi, India


On Thu, May 1, 2014 at 12:08 AM, Eric Altshuler <ela at cola.iges.org> wrote:

> Dear Amulya,
>
> The grads scripting language does not support directly accessing the
> values of data variables (either defined or from a dataset). In your 'if'
> statements, the variables 'a' and 'b' refer to script variables, not data
> variables. You need to first obtain the values of your *defined*variables a and b, then assign these values to script variables. Just
> before each 'if' statement in your script, insert the following lines:
>
> 'display a'
> a=subwrd(result,4)
> 'display b'
> b=subwrd(result,4)
>
> It may be a bit confusing, but the script variables 'a' and 'b' (i.e.
> those assigned values using subwrd function) are NOT the same as the data
> variables a and b (i.e. those in the 'display' commands).
>
> Best regards,
>
> Eric L. Altshuler
> Research Scientist
> Center for Ocean-Land-Atmosphere Studies
> 253 Research Hall, Mail Stop 6C5
> George Mason University
> 4400 University Drive
> Fairfax, VA 22030 USA
>
> E-mail: ela at cola.iges.org
> Phone: (703) 993-5725
> Fax: (703) 993-5770
>
>
> ------------------------------
> *From: *"Amulya Chevuturi" <amulya.chevuturi at gmail.com>
> *To: *"GrADS Users Forum" <gradsusr at gradsusr.org>
> *Sent: *Wednesday, April 30, 2014 12:18:33 AM
> *Subject: *[gradsusr] Contingency Table
>
>
> Dear Grads Users
>
> I am trying to build contingency table for model verification using grads.
> Currently my model and observation are both at exactly same resolution. So
> I have written the following script. But it is not giving me the count of
> Yes/Yes, No/No etc correctly. How am I supposed to build contingency table
> using grads if someone can please help.
>
> Following is the script.
>
> 'reinit'
>
> 'open model.ctl'
> 'set t 3'
> 'set y 57 208'
> 'set x 72 228'
> 'define a = rain'
> 'close 1'
>
> 'open observation.ctl'
> 'set t 3'
> 'set y 57 208'
> 'set x 72 228'
> 'define b = prec'
>
> n1=0
> n2=0
> n3=0
> n4=0
> j=72
> while (j<=228)
> 'set y 'j
> i=57
> while (i<=208)
> 'set x 'i
> if(a>0&b>0)
> n1=n1+1
> else
> if(a<=0&b<=0)
> n2=n2+1
> else
> if(a<=0&b>0)
> n3=n3+1
> else
> if(a>0&b<=0)
> n4=n4+1
> endif
> endif
> endif
> endif
> i=i+1
> endwhile
> j=j+1
> endwhile
> say n1
> say n2
> say n3
> say n4
> 'close 1'
>
> Or is anyother method available for making contingency tables for forecast
> verification with grads?
>
> Please let me know.
>
> Regards
> Amulya Chevuturi
>
>
>
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