MATLAB 中的 Ode45

Question

I'm quite new to MATLAB and im trying to integrate two functions using the ode45() function. My code:

[w,x] = ode45( @(w,x) ( TSII - TFII ) * w , [0 2], 0 );

Where TSII and TFII are column vectors 1x151 containing the values of my two functions. w does not have any value yet, but I've tried making it a column vector full of zeroes length 1x151 and that did not solve my problem.

I get the following error message:

@(W,X)(TSII-TFII)*W returns a vector of length 151, but the length of initial conditions vector is 1 .

The vector returned by @(W,X)(TSII-TFII)*W and the initial conditions vector must have the same number of elements.

Is it possible to change the initial conditions vector to the same length as TSII and TFII ?

Or, should I use a loop with ode45() inside to make the 151 values?

Answer 1

I am guessing a bit, but give it a try:

ode45() would like your anonymous function @(w,x) to interpolate the function value at position x . If TSII and TFII are tabular function values as you write, it will not return the expected result.

You should use something like interp1(TSII,x) instead of TSII . your function should look like:

@(w,x) ( interp1(TSII,x) - interp1(TFII,x) ) .* w

Also note the .* for the element wise multiplication.