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

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

OK, I understand the concept of key and curve point.

How can it be done in iteration?

Regards,

On Mon, Mar 15, 2010 at 11:27 AM, sfeam (Ethan Merritt)
<eam...@gm...> wrote:
> On Sunday 14 March 2010, hon fui lee wrote:
>> 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.
>
> I was not clear enough.  Please see "help colorspec"
>
> The idea is that the 'Z' in "lc palette Z" stands for either
> "frac <value>" where <value> runs from 0 to 1 and represents
> a sample on the current palette,  or "cb <value>" where
> <value> is drawn from the range of the current colorbox.
>
>> 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.
>
> Fine.  So let's assume your student's ages run from 20 to 30.
> Then we have
>   set cbrange [20:30]
>   plot 'student1' using ... with lines lc cb 21,
>        'student2' using ... with lines lc cb 25,
>                'student3' ...
> and so on.
>
>> 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?
>
> You have asked it to color the lines by z value.
> Each point or line segment has a z value.
> But what is the z value of the key?  It has none.
>
>        Ethan
>
>
>> 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
>



-- 
hon_fui