Why I am getting error message when I try to define line specs of a plot?

Hello

I am trying to fit a curve to a data and create a plot. The code creates the plot, but when I define the line width, it gives error message;

f = fittype('a + b*log(x)',...
    'dependent',{'y'},'independent',{'x'},...
    'coefficients',{'a','b'});
fit1 = fit( time1, strain1, f )

plot(fit1,'k-','LineWidth',2)

The error message I got is below;

fit1 = 

     General model:
     fit1(x) = a + b*log(x)
     Coefficients (with 95% confidence bounds):
       a =     0.04434  (0.04336, 0.04532)
       b =    0.004645  (0.004399, 0.004891)
Index exceeds matrix dimensions.

Error in cfit/plot (line 66)
      ydata = ydata(idx);

It does not give any error message if I do not define 'LineWidth'.

Waiting for your kind help.

Regards

Answer 1

[Walter Roberson]

plot() for cfit objects is not the generalized plot function. It does not accept LineWidth parameters.

You should proceed like

h = plot(fit1, 'k-');
set(h, 'LineWidth', 2);

[Suleyman Deveci]

Thanks for your help Walter. That worked well.

Answer 2

[A. Sawas]

This will solve the problem.

p = plot(fit1,'k-');
p.LineWidth = 2;

Answer 3

[TADA]

You are using an overload of plot that accepts a cfit object

https://www.mathworks.com/help/curvefit/cfit.plot.html

this overload doesn't support all the functionality of the regular plot function

you can calculate the fit data and plot that, or you can take a handle of the curve and fix that later:

time1 = (1:100)';
strain1 = log(time1);

f = fittype('a + b*log(x)',...
    'dependent',{'y'},'independent',{'x'},...
    'coefficients',{'a','b'});
fit1 = fit( time1, strain1, f );

% calculate the fit vector and plot numbers
y = feval(fit1, time1);
plot(time1, y, 'k-', 'LineWidth', 2);

% manipulate the curve handle after plotting
h = plot(fit1,'k-');
h.LineWidth = 2;