Re: [ferret_users] Question about selecting specific data to plot in a histogram

[John Donners <j.donners@xxxxxxxxxxxxx>]

Hi Anthony,

what you need to do is to make a new variable where the correct  
months are masked:

let evap_l=l[gt=evap]
let evap_djf=if mod(evap_l,12) le 2 then evap

the variable evap_djf should contain the evaporation only in the  
months that you need.
The histogram can then be plotted for the variable evap_djf.

For a specific location, you could use:

let evap_loc=evap_djf[x=74W,y=40N]

and make the histogram for this variable.

histograms for a part of your dataset could be done as follows with a  
REPEAT:

repeat/range=1:1198/name=cnt (let evap_part=evap[l=`cnt`:`cnt 
+2`@sum] ; .. [plot histogram] .. )

although I guess that you need to average the values (@ave instead of  
@sum), otherwise the values
are 3 times larger. Or leave out the @-operator to get the histogram  
for three separate months plotted together.

Cheers,
John


On 31 May 2007, at 22:44, toine379@xxxxxxxxxxxxxxxx wrote:

> My name: Anthony DeAngelis
> Ferret version: 5.81
> Accessing Ferret: Linux(g77) 2.4.21-32 - 07/13/05
>
> I am a college student working with a professor this summer on a  
> research
> project, and part of our research requires plotting histograms with  
> a very
> specific data set.  How do I select specific data points to include  
> in a
> histogram?
>
> For example, I am using a data set which includes the variable  
> evap, the
> surface evaporation rate, which depends on i, j, and l, where i:  
> [1:144],
> j: [1:90], and l: [1:1200].
>
> I know how to make a simple histogram, but I do not know how to get  
> the
> exact one I want from specific points along the l axis data.  I  
> want to
> make a histogram where I specify x and y by specific points, such  
> as 74W
> and 40N, and for l, only plot points where l=  
> 1,2,12,13,14,24,25,26, and
> so on up to 1200, following that pattern.  Additionally, how would  
> I plot
> a histogram where I group parts of l together, such as l= 1:3@sum,
> 2:4@sum, 3:6@sum, etc up to 1200.  I have attempted to do this by  
> typing
> in a similar syntax but it does not work.  I have tried to do this  
> through
> the repeat function, if/then statements, and other methods and I still
> can't seem to get it.  I have searched the user's guide to find
> information about this but still failed.  Please show me how to do  
> this or
> direct me to a specific place in the user's guide where this  
> material is
> covered.
>
> Thank you for you help.