Parse error: usage might be invalid MATLAB syntax

Question

Abraham 2018-10-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/424856-parse-error-usage-might-be-invalid-matlab-syntax

评论： Walter Roberson 2018-10-19

So, I'm to write a function called trapint.m that takes data sample locations and function samples at those locations as input and returns an approximation of the integral over the sample range based on the trapezoidal rule. This is the detail of the instruction

This is what I did:

function I=trapint(x,fx)
N= max(size(fx));
N= max(size(x));
If n==N;
If isvector(x)==isvector(fx)==1;
If Isnumeric(x) == isnumeric (fx)==1;
h=(fx(1)-fx(N))/N;
i=2; y=0;
while i<=n-1 %%for summation of middle no between a and b
y = y+(fx(i));
i=i+1;
end
I=h/2*(fx(1)+2*y+fx(N));
ans=double(ans);
end
else
sprintf('error = x and fx are not of same length')
end
else
sprintf ('error =x and fx are not vectors')
end
else
Sprintf ('error= either data contained other than numerical value')
end

I got parse errors and invalid characters in lines 27,31,33,35,39 and 41. Thanks in advance

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Walter Roberson 2018-10-19

在 MATLAB Online 中打开

If isvector(x)==isvector(fx)==1;

tries to invoke a function named If with a single argument, like

If('isvector(x)==isvector(fx)==1');

You probably do not have a function named If. You probably do not have a function named Sprintf either.

MATLAB is case sensitive.

Your code has several Zero-Width Space characters https://www.fileformat.info/info/unicode/char/200B/index.htm . You can't see them, of course...

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Answer 1

madhan ravi 2018-10-19

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/424856-parse-error-usage-might-be-invalid-matlab-syntax#answer_342188

编辑：madhan ravi 2018-10-19

在 MATLAB Online 中打开

fx=1:10 %an example of the vectors
x=10:20
I  =   trapint(x,fx)
function I=trapint(x,fx)
N= max(size(fx));
N= max(size(x));
if nargin(trapint)<2
    error('inputs must be two ')
if size(fx)~=size(x)
    error('not same size')
if isvector(x)~=1 & isvector(fx)~=1
    error('not vectors')
h=(fx(1)-fx(N))/N;
i=2; y=0;
while i<=n-1 %%for summation of middle no between a and b
y = y+(fx(i));
i=i+1;
end
I=h/2*(fx(1)+2*y+fx(N));
I=double(I); % whats ans here???
end
end
end
end