[ferret_users] apparent bug in frequency_histogram.jnl

[Keith Lindsay <klindsay@xxxxxxxx>]

Hi,

I think I have found a bug in frequency_histogram.jnl. In particular 
instances, the bars are shifted by two bins horizontally.

The attached CDL file leads to a demonstration of the problem.

The commands

sp ncgen -b hist_test.cdl
set data hist_test.nc
go frequency_histogram.jnl var .5 4.5 .1 weight

produce the attached figure. The bins should be centered over 1, 2, and 
3, but they are shifted to the right by two bins.

It seems to be problem with missing values in the expression and weight 
leading to lines in the generated frequency_h.raw file with no space 
between the value pairs, and then the frequency.awk script generates 
extra lines of output which ends up shifting the bars.

If I replace the following lines of frequency_histogram.jnl

list/nohead/form=(F10.0,1PG14.7)/file=frequency_h.raw index, wt_index
list/nohead/form=(F10.0,1PG14.7)/file=frequency_h.raw/append vn+1,0  ! MAX index + 1

with

list/nohead/form=(F10.0,x,1PG14.7)/file=frequency_h.raw index, wt_index
list/nohead/form=(F10.0,x,1PG14.7)/file=frequency_h.raw/append vn+1,0  ! MAX index + 1

I get the expected results.

This does not appear to be a problem with frequency_histogram2.jnl

Keith

******************************************************************
Keith Lindsay                http://www.cgd.ucar.edu/oce/klindsay/
email: klindsay@xxxxxxxx   phone: 303-497-1722   fax: 303-497-1700

netcdf hist_test {
dimensions:
	x = 4 ;
variables:
	float x(x) ;
	float var(x) ;
	float weight(x) ;
		weight:_FillValue = 1.e+36f ;
data:

 x = 1, 2, 3, 4 ;

 var = 1, 2, 3, _ ;

 weight = 1, 2, 3, _ ;
}

Attachment: hist_test_fig.gif
Description: GIF image