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

Sun Apr 12 02:45:07 CEST 2020

Federico,

I am extracting the values of the vectors (vv12 and vt12) from a logic in
which it takes data from a spreadsheet that was generated using specific
software. The vectors (vv12 and vt12) represent an efficiency curve within
the torque x speed plane, I have eleven more of these vectors that vary in
size. I believe that I do not have a role in which one depends on the other
directly. I tried to follow your first reasoning and arrived at a routine
that does not report errors but is not smoothing my curve either, follow
the routine:

clcclearvt12 = [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]
c = size (vt12)a = 1b = c(2)n = c(2)x = linspace (a, b, n)
[yvt,dvt] = lsq_splin(x,vt12,linspace (a,b,n))[yvv,dvv] =
lsq_splin(x,vv12,linspace (a,b,n))
ys=interp(linspace (a,b,n),linspace (a,b,n),yvt,dvt)xs=interp(linspace
(a,b,n),linspace (a,b,n),yvv,dvv)
plot (ys,xs,'r')xlabel ('Speed (rpm)')ylabel ('Torque (Nm)')title
('Torque x speed values')

Any idea how I can proceed with my goal of smoothing the curve to use
the color map later?

On Sat, Apr 11, 2020 at 9:18 PM Federico Miyara <fmiyara at fceia.unr.edu.ar>
wrote:

>
> 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>
> 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>
>>
>>
>>
>> --
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