# Taking a derivative of a function and plotting it over a specified length

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Aaron on 19 Feb 2013
Here is what I have so far. Keep getting errors. Trying to take the derivative of meanline and then plot this function over the length of x.
%Given variables
x = 0:0.1:2;
c = 2;
%Given Functions
meanline = c*(((x./c).^0.9)-(x./c));
thickness_distribution = ((2*c)/5)*(((x./c).^0.5)-(x./c));
%Solving
syms x
slope_meanline = diff(meanline);
%Plot
plot(x,slope_meanline)

Jonathan Epperl on 19 Feb 2013
Are you assigning the variable x before you call syms x? Probably, and that's probably the problem.
If you really want further help, you should post the error messages you are getting, "Keep getting errors" is not very helpful.
Aaron on 19 Feb 2013
Tried putting the syms x before assigning the variable X and got this message.
??? Error using ==> plot
Vectors must be the same lengths.
Error in ==> wind_hw5 at 20
plot(x,slope_meanline)

Youssef Khmou on 19 Feb 2013
Edited: Youssef Khmou on 19 Feb 2013
hi Aaron
you get error because because slope_meanline is numeric and you want to plot numeric vs symbolic , there are many ways to solve the problem, try this :
c=2;
syms x;
meanline = c*(((x./c).^0.9)-(x./c));
slope_meanline=diff(meanline);
range=[0 10];
ezplot(slope_meanline,range )