(R2011a) Hello, (I'm new to matlab) when using the diff function to take the nth order derivative of a function, one can use this syntax:
f = % some function of x %
d = diff( % function (f) to be differentiated % , % number (n) of times to differentiate %);
where n is some integer.
However, if I define a function of some other variable, namely :
s = ceil(y * (heaviside(y) - (2 * heaviside(y) * heaviside(-y))))
which outputs only non-negative integers, and then insert that function in place of n in the diff function, which looks like:
d = diff( % function of x to be differentiated % , s);
then the diff function will not differentiate our function (of x) s times, and will instead return some error on the line of where s is defined.
I am trying to create a 3D plot that displays the various s-order derivatives of and arbitrary function (of x), wherein each plane of the form y=n, where n is some integer, contains the nth order derivative of the function (of x).
How can I put some function of either and array or a symbol into the second parameter of the diff function in order to achieve what I want?
Thanks, Mike
This is ultimately what I'd like to run:
% First we define x and t as symbols, and y as an array.
syms x;
syms t;
y = linspace (-3,3);
% We also define a mesh so that we can late plot z as a function of both x
% and y.
[x,y] = meshgrid(x,y);
% Next we define some function of x.
f = x;
% Then we define the ceiling of the unit step function multiplied by y.
s = ceil(y * (heaviside(y) - (2 * heaviside(y) * heaviside(-y))));
% After that we define j as the sth-order derivative of f, where s is some
% integer
j = diff(f,s);
% Now we define the other factor of the integrand as L.
L = (x-t)^( -1 -y -s);
% Now we define the gamma function adjusted for our uses.
G = gamma( s - y );
% Now we define a function z as the integral from 0 to x of j multiplied by L with
% respect to t, all divided by G.
z = int(j*L,t,0,x)/G;
%Finally, we plot x, y, and z in a 3d mesh
ezsurf(z);
And here are the two errors I receive when I run it:
??? Error using ==> mtimes
Inner matrix dimensions must agree.
Error in ==> fracint at 14
s = ceil(y * (heaviside(y) - (2 * heaviside(y) * heaviside(-y))));
Should I have different definitions for x, y, and t than I currently do? Also, am I simply using incorrect syntax or is there a bigger problem (regarding the errors) than I know? Thanks, Mike