Need help: Script working in 2012b but not 2013b???

2013 10 19
3 个回答
回答已采纳
更新时间：2013 10 22
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Been working my way through a matlab tutorial. The scripts in the tutorial all have a similar layout:
if true
function solve_bernoulli
% Function to solve dy/dt = (t*y^4+2y)/6
% from t=tstart to t=tstop, with y(0) = initial_y
% Define parameter values below.
tstart = 0;
tstop = 20;
initial_y = -2;
[t_values,sol_values] = ode45(@diff_eq,[tstart,tstop],initial_y);
plot(t_values,sol_values);
function dydt = diff_eq(t,y) % Function defining the ODE
dydt = (t*y^4+2*y)/6;
end
end
end
The layout is as below:
  • function function_name
  • %stuff in the function
  • %May even include an actual embeded function (as the example above has)
  • end
Every time I run it I get the error:
"The selected section cannot be evaluated because it contains an invalid statement"
and in the command window:
" function solve_bernoulli | Error: Function definitions are not permitted in this context."
HOWEVER , this script works in the tutorial writings computer using 2012b. So how can this not work on my 2013b version???
Need help as this is driving me nuts!

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mark
mark 2013-10-19

0 个投票

Okay, I found out why, and it revolves around me being a lazy tw@;
I don't normally " save " scripts — instead I choose to use " Run and Advance " as it generally runs scripts fine, allowing you to test them out before you save it. It seems that, although I was saving the function first, using " Run and Advance " on a function doesn't work (at least a function in the form above). You actually need to use the more general, and obvious, " Run ".
I feel like an idiot but I'm glad I found it out instead of giving up on it.

更多回答（2 个）

Daniel Shub
Daniel Shub 2013-10-19

1 个投票

The above code will not work in ANY version of MATLAB because
if true
function solve_bernoulli
...
is not valid. The FUNCTION keyword can only be used in an m file. Further, the first line of code in the m file must begin with the FUNCTION keyword. Despite your claims, removing
function solve_bernoulli
and the corresponding end will not solve the problem since it will leave
function dydt = diff_eq(t,y)
in the middle of the m file, which again is not valid (or you are leaving out part of the code).

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mark
mark 2013-10-19
编辑：mark 2013-10-19
I'm sorry but it works.
if true
function solve_bernoulli
% Function to solve dy/dt = (t*y^4+2y)/6
% from t=tstart to t=tstop, with y(0) = initial_y
% Define parameter values below.
tstart = 0;
tstop = 20;
initial_y = -2;
[t_values,sol_values] = ode45(@diff_eq,[tstart,tstop],initial_y);
plot(t_values,sol_values);
function dydt = diff_eq(t,y) % Function defining the ODE
dydt = (t*y^4+2*y)/6;
end
end
end
Copy and paste that into a script. Save it. Then click the green play button.
My issue was that I wasn't playing the script properly. I don't quite know why the guy writes scripts in this way, but he does.
Daniel Shub
Daniel Shub 2013-10-22
No it doesn't ...
>> temp
Error: File: temp.m Line: 3 Column: 5
Function definitions are not permitted in this context.
MATLAB has never permitted code like this.

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mark
mark 2013-10-19

0 个投票

*writers computer
I should probably add that I can get the script to work if I remove the "function function_name" part and reorganise the script. But, I don't understand how it doesn't work on my computer.

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