How to extend the fitting curve in command

I want to fit a set of data with custom function. I wrote:

"" Wavelength=VarName3

Wavelength =

   1.0e+03 *

    0.6176
    0.6273
    0.6371
    0.6482
    0.6572
    0.6684
    0.6801
    0.6902
    0.7014
    0.7103
    0.7218
    0.7333
    0.7431
    0.7524
    0.7608
    0.7721
    0.7825
    0.7934
    0.8044
    0.8179
    0.8267
    0.8365
    0.8469
    0.8565
    0.8658
    0.8771
    0.8907
    0.9028
    0.9110
    0.9215
    0.9316
    0.9407
    0.9503
    0.9605
    0.9707
    0.9797
    0.9945
    1.0004
    1.0115

>> Intensity=VarName4

Intensity =

795.5000
788.5000
773.5000
727.0000
716.5000
694.5000
656.5000
626.5000
600.0000
595.5000
593.0000
589.5000
545.0000
540.5000
516.5000
509.0000
475.5000
470.0000
432.5000
394.0000
369.0000
357.5000
355.5000
329.0000
315.5000
307.0000
302.5000
300.0000
293.0000
291.0000
279.0000
275.0000
269.0000
265.0000
242.0000
240.0000
234.5000
233.0000
224.0000

>> f = fit(Wavelength , Intensity, 'a*100000000000*(x.^-5)*(exp(1.4E07/(T*x))-1).^-1', 'StartPoint', [10000,0.0014] )

f =

     General model:
     f(x) = a*100000000000*(x.^-5)*(exp(1.4E07/(T*x))-1).^-1
     Coefficients (with 95% confidence bounds):
       T =        8917  (8406, 9428)
       a =   8.682e+06  (7.45e+06, 9.913e+06)
>> plot( f,Wavelength,Intensity,'o' )
""
And I got the plot as follow

Now I want to extend the fitting curve further like this figure:

What should I do??? I need your help

Answer 1

[Ahmet Cecen]

All you need to do is calculate Y axis for that entire range using the fit you calculated. Pass x=0:1:1400 through f(x), then plot x vs f(x).

[Thi Na Le]

How do I calculate y-values when I just have limitd values of x? Thank you :)

[Ahmet Cecen]

No, I mean, you trained your fit on the dataset you have, and found f using fit function. Now you want do:

x=0:1:1400;
yhat=f(x); 
plot(x,yhat);

unless I am not getting your question right.

[Thi Na Le]

yeah. you got my question right. But when I added x=0:1:1400; yhat=f(x); plot(x,yhat); to my program, I only got the curve without data points:

I need data points to be appeared in the graph. Did I do something wrong?

[Ahmet Cecen]

OOOH. Use the hold command to overlay the two figures. Say:

 x=0:1:1400;
 yhat=f(x); 
 plot(x,yhat); %As before
 hold on;
 plot(X,Y,'o');%Check  http://www.mathworks.com/help/matlab/ref/linespec.html for marker types.

X and Y would be your actual training data, so I think X is wavelength and Y is intensity. Use the GUI afterwards to polish the figure.

[Thi Na Le]

Thank you. I already got the point. I just wrote: plot (Wavelength,Intensity, 'ro', x, yhat,'r'); :))))))

Answer 2

[Amr Hashem]

try:

 hold on

before the extended plotting

Answer 3

[Sagar bendre]

HI, I am plotting a PSD with pwelch. I want to increase in max range of wavelength. Ufortunatelly the range by software is holding till 3.14 cyc/m. I want to see max wavelength of my data..

pl let me know...