[Scilab-users] spline and color plot on the chart

[Federico Miyara]

Daniel,

I'm afraid I was a bit confused with your application case.

I assumed that there was an independent variable such as time or other 
which the other two, vt12 and vv12, depend on. If this were the case, 
the expected graph could be a curve or rather a trajectory with some 
hysteresis.

But if your data are just measurements in no particular order of what is 
a functional relation of one variable respect to the other, for instance 
vt12 = f(vv12), then the approach is different. You should basically 
sort the independent variable in increasing order using gsort and apply 
the same sorting to the dependent variable:

[x, I] = gsort(vv12,"g","i");
y = vt12(I);

Then you can proceed to interpolate with spline or lsg_splin.

Regards,

Federico Miyara


On 10/04/2020 21:05, Daniel Stringari wrote:
> Federico,
>
> I appreciate the help. Below is a list of the code on which I try to 
> plot the data with Isq_splin:
>
> c = size (vt12)
> a = 0
> b = c (1) // c (1) = 16
> n = c (1)
> x = linspace (a, b, n)
> [y, d] = lsq_splin (vt12, vv12, x ')
> plot (y, d, 'r')
> xlabel ('Speed (rpm)')
> ylabel ('Torque (Nm)')
> title ('Torque x speed values')
>
> //vt12 = 5350.3 5380.19 5410.08 5439.96 4149.5 4179.35 3756.57 3602.73 
> 3568.12 3597.85 3681.91 3711.59 6143.24 6172.86 6202.49 6232.1
> //vv12 = 40.16   39.93   39.71   39.49   69.04   68.54   95.32 119.26 
>   140.49   139.32   155.62   154.37   93.27   92.82 92.38   91.94
>
> but I'm getting the error: lsq_plin: There are not enough points to 
> adjust.
>
> Does anyone understand what could be wrong?
>
> On Wed, Apr 8, 2020 at 12:54 AM Federico Miyara 
> <fmiyara at fceia.unr.edu.ar <mailto:fmiyara at fceia.unr.edu.ar>> wrote:
>
>
>     Daniel,
>
>     You may try with lsq_spline, which unlike ordinary spline, doesn't
>     fit the data exactly, and it doesn't need the data with any
>     particular order.
>
>     But trying to understand your graph, it seems that you should
>     parametrize two variables independently, each one with respect to
>     the index. Something like this:
>
>     x = [x1, x2, ..., xn]
>     y = [y1, y2, ..., yn]
>
>     Then you approximate x vs 1:n and y vs 1:n using spline or
>     lsq_splin. Finally you plot xs vs ys (the smoothed versions of x
>     and y)
>
>     Regards,
>
>     Federico Miyara
>
>
>     On 07/04/2020 22:48, Daniel Stringari wrote:
>>     Good night friends,
>>     I wrote an email before, but I believe that I was not clear in my words and
>>     so I will write more clearly.
>>
>>     In this annex 1, I have the graph I am generating. Basically I am extracting
>>     values of x (speed) and y (torque) from excel and generating vectors of x []
>>     and y [] to plot internal lines. I want to smooth these lines, but the
>>     functions of the scilab are only for growing points. I thought about
>>     creating cubic splines manually, but I don't know how to do it. Can anybody
>>     help me ?
>>
>>     In addition, I would like to color my chart with level colors according to
>>     the colorbar, but I am not able to implement contour2d for this case.
>>
>>     thanks.
>>
>>     <http://mailinglists.scilab.org/file/t498028/annex_1.png>  <http://mailinglists.scilab.org/file/t498028/annex_1.png>  
>>
>>
>>
>>     --
>>     Sent from:http://mailinglists.scilab.org/Scilab-users-Mailing-Lists-Archives-f2602246.html
>>     _______________________________________________
>>     users mailing list
>>     users at lists.scilab.org  <mailto:users at lists.scilab.org>
>>     http://lists.scilab.org/mailman/listinfo/users
>>
>
>     _______________________________________________
>     users mailing list
>     users at lists.scilab.org <mailto:users at lists.scilab.org>
>     http://lists.scilab.org/mailman/listinfo/users
>
>
> _______________________________________________
> users mailing list
> users at lists.scilab.org
> http://lists.scilab.org/mailman/listinfo/users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.scilab.org/pipermail/users/attachments/20200411/d46ddfbd/attachment.htm>