Increasing number of points in a plot without ruining the shape

How can I make this plot look like

this plot but instead of reducing points I want to increase data points in red plot to 20. Using linspace or interp1 is giving me a straight line. I want to conserve the shape of the plot and increase the number of points in the plot.

Answer 1

[darova]

Is it correct? (Not tested)

x1red = linspace(xred(1),xblue(end),20);            % more points for red curve
    % scaling red curve (make it as long as blue one)
Lred = xred(end) - xred(1);
Lblue= xblue(end) = xblue(1);
xred_scaled = xred(1) + (xred-xred(1))*Lblue/Lred;
y1red = interp1(x_red_scaled,yred,x1red);
plot(xblue,yblue,'b')
hold on
plot(x1red,y1red,'r')
hold off

Answer 2

[Stephen23]

Try using method spline or pchip and see if they do what you want:

interp1(...,'pchip')

https://www.mathworks.com/help/matlab/ref/interp1.html#btwp6lt-1-method

[Stephen23]

Writing "it's not working" tells us nothing. If you want further help then please:

• tell us if you are extrapolating the data.
• show the exact code that you are using.
• upload sample data in a .mat file.
• show or explain how the expected output is different to what you get.