Re: bug in histogram plot with binary data?

[Daniel J S. <dan...@ie...>]

Ethan Merritt wrote:
> On Wednesday 30 January 2008 12:42, Ethan Merritt wrote:
> 
>>I help is needed from someone more familiar with the binary data modes.
>>Anyone care to take over this bug report?
> 
> 
> 
> The following one-liner makes your test case work.
> 
> However, I am *not* applying this to CVS because I just don't understand
> the code well enough.  The binary read code at this point is not parallel 
> to the ascii input code, which simply does ++df_datum as it goes.
> Why is this different?  Is it correct?  Will it break other things?
> I don't know.
> 
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> --- gnuplot/src/datafile.c      2008-01-25 12:59:41.000000000 -0800
> +++ gnuplot-cvs/src/datafile.c  2008-01-30 23:01:30.000000000 -0800
> @@ -4937,7 +4937,7 @@
>                 }
>             }
>         } else { /* Not matrix file, general binray. */
> -           df_datum = point_count;
> +           df_datum = point_count+1;   /* EAM DEBUG */
>             if (i != df_no_bin_cols) {
>                 if (feof(data_fp)) {
>                     if (i != 0)
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> 
> 
>>On Wednesday 30 January 2008 12:15, Ralf Juengling wrote:
>>
>>>Here you go. The binary data is in intel pentium endianess
>>>(whatever that is).
>>
>>Thanks. So far as I can tell from a quick test, the problem is
>>not specific to histograms.  Any other plot type also gets incorrect
>>x coordinates when using the binary read command on that data file.
>>If I dump the contents after reading them in, I get this:
>>
>>gnuplot>  set style data linespoints
>>gnuplot>  plot "histdata.bin" binary array=1:8 format="%int" using 1
>>gnuplot> set table
>>gnuplot> replot

The array=1:8 specification indicates that there are two single dimensional arrays of data, one 1 element long, another 8 elements long.  However, that doesn't seem to match what the user is intending if there are only 7 data points.  (There should be nine.)  Perhaps the user just wants array=7.

>>
>># Curve 0 of 1, 7 points
>># Curve title: ""histdata.bin" binary array=1:8 format="%int" using 1"
>># x y type
>> 0  102  i

The above would be the first "line" of data.

>> 0  42  i
>> 1  38  i
>> 2  28  i
>> 3  26  i
>> 4  108  i
>> 5  156  i

The rest constitutes the second "line" of data, even though there isn't enough to fill out eight elements.

Both of the above start at zero.  If you want the inherent x value assigned to begin at 1 with the above patch, that's fine.  (Is that what the ASCII data default is?  Then matching the two would be good.)

The thing that is a bit of a problem is what the table displays.  Curve 0 of 1 should maybe be curve 1 of 1, but more importantly, one might expect it to be Curve 1 of 2 and Curve 2 of 2 if the user specifies array=L1:L2, where L means "length".

However, this trait isn't unique to binary data.  Try the following:

Terminal type set to 'x11'
gnuplot> set table
gnuplot> plot '-' with lines
input data ('e' ends) > 1
input data ('e' ends) > 2
input data ('e' ends) > 3
input data ('e' ends) > 4
input data ('e' ends) >
input data ('e' ends) >
input data ('e' ends) > 5
input data ('e' ends) > 6
input data ('e' ends) > 7
input data ('e' ends) > 8
input data ('e' ends) > e

# Curve 0 of 1, 9 points
# Curve title: "'-'"
# x y type
 0  1  i
 1  2  i
 2  3  i
 3  4  i
 0  0  u
 0  5  i
 1  6  i
 2  7  i
 3  8  i

gnuplot>

The x-values assigned begin at 0.  There is an extra "undefined" in the middle, which doesn't happen for binary data.  Note that the comment says curve 0 of 1 (perhaps that is correct, i.e., multiple scan lines but still a single curve).  But 9 points instead of 8?

Dan