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

[toine379@xxxxxxxxxxxxxxxx]

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.