RE: key error in 2D plot line with color palette by hon fui lee

[hon f. l. <ho...@gm...>]

Tried your suggestion. The "lc palette Z" introduces error like " line
XX: ';' expected".
"lc Z" is OK but not as palette, discrete color instead. Same as "lc
variable" Eg. of my Z value ranges from 0.105 to 0.331.

Let me give you a better example. A study on a group of university
student on their age and performance.
Student A: Age 21
Hour attending class subject 1= 10 hours : Score=70
Hour attending class subject 2= 12 hours : Score=80
.
.
.
.
Student B: Age 25
Hour attending class subject 1= 10 hours : Score 55
Hour attending class subject 2= 20 hours : Score 60
.
.
.
.

Let plot hour attending class subject (x) vs score (y). Each curve is
colored according to the age to see any trend.

In my earliest post, notice linespoints give correct color and symbol
according to the plot/key, just like the curve itself. Only the line
color is wrong.
If the plot can do color palette/gradient on the curve correctly(or
may be incorrectly) why not the key?


Thanks.

On Thursday 11 March 2010 23:30:28 hon fui lee wrote:
> I'm trying to do a 2D lines/linespoint plot with linecolor from 3rd
> column as color palette.
> All are OK except the key does not proper linecolor. See sample
> command file and sample output (pdf).
> I'm using gnuplot version 4.5 (development) on Windows.
>
> Is that a bug or feature? Thanks.

I think it is a mis-expectation.

Your lines happen to each have a constant Z value, which you can think of
as a color value, so for your particular plot each entire line is a
single color and it would make sense for the sample line segment in the
key to be that same color.

But how is gnuplot supposed to know this?  In general each point could
have a different Z value and each line would have many segments with
various colors.  Which of these colors would you put in the key?

If you know in advance that each line has a constant Z value, maybe
you can revise the plot command so that instead of
   plot 'foo' using 1:2:3 lc palette
you use
   Z = constant_z_for_this_line
   plot 'foo' using 1:2 lc palette Z

For this you would have to read in the Z values before issuing the
plot command.  That may or may not be possible in your particular
plotting scenario.

	Ethan

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-- 
hon_fui