Plotting an equation raised to a variable.

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Adam Hermon
Adam Hermon 2019-12-14
编辑： Ridwan Alam 2019-12-17
Hello, I am trying to plot an equation that has a variable as an exponent, but I am getting errors that the matrix dimensions must agree. Is there a specific way in matlab that this has to be done for it to graph? Any help would be appreciated, thanks in advance.
n = 0:2:10;%first 6 non-zero derivatives
a_n = 12*(40).^n.*((-1).^(n/2))./(factorial(n));%first 6 non-zero terms
% Functions to plot
t = linspace(0,0.2,400);%select points in the range to plot
fun1 = a_n(1)*t.^0;%n=0
%Want to implement fun1 like this but that is having errors.
fun1 = a_n(1)*(t.^(n))
  2 个评论
Ridwan Alam
Ridwan Alam 2019-12-14
what is a_n(1) and t? I am assuming your n is the variable array, right?
Adam Hermon
Adam Hermon 2019-12-14
Hey, thanks for your reply, I should have made that clearer. a_n is a general expression and n is the array of values I need to use. I know the first function can just be written as a_n(1)*t^n, but it doesn't work as like when I use zero.
n = 0:2:10;%first 6 non-zero derivatives
a_n = 12*(40).^n.*((-1).^(n/2))./(factorial(n));%first 6 non-zero terms
% Functions to plot
t = linspace(0,0.2,400);%select points in the range to plot
fun1 = a_n(1)*t.^0;%n=0

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回答（1 个）

Ridwan Alam
Ridwan Alam 2019-12-15
编辑：Ridwan Alam 2019-12-17
fun1 = a_n(1)*(t.^(n))
.^ is a pointwise (elementwise) operation, that means it operates on arrays of same length or one of the operator needs to be an scalar. In your code, length(n) is 6 and length(t) is 400. Hence, the error is thrown.
I assume you are looking for something like this:
fun1 = a_n(1)*(t.^(n(1)));
plot(t,fun1); hold on;
fun2 = a_n(2)*(t.^(n(2)));
plot(t,fun2);
But if you really want to variables on the right side of fun1, you can make t the same size of n:
t = linspace(0,0.2,length(n));
fun1 = a_n(1)*(t.^(n)); % now n and t are arrays of same size
Hope this helps.

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