how to solve equation for a given matrix

Hi everybody

I have got equation which is ;

Eq = 0.4075*exp(-((e-14.87)/11.39).^2) + 0.5621*exp(-((e-18.64)/27.74).^2);

e is a 100*1 double matrix.

I would like to use the value of each row as an input to my function and save the results as matrix again. I used solve command, I could get any results.

Any suggestion is highly appreciated.

Thanks!!

[madhan ravi]

just loop through e and solve the equations?

[engineer]

thanks for the answer. Can you show or refer me an axample ?

[madhan ravi]

Ah sorry which variable are you the solving for?, you say you already have e in hand?

[engineer]

Yes I have it 'e' as 100*1 double matrix. I just need to implement each value into the function and obtain the results as another matrix.

[madhan ravi]

e = .... 100 X 1 values
Eq = 0.4075*exp(-((e-14.87)/11.39).^2) + 0.5621*exp(-((e-18.64)/27.74).^2); % doesn't this get you the required results?

Answer 1

[Adam Danz]

What's wrong with what you've already got?

%Vector method
e = rand(100,1)*10; 
Eq = 0.4075*exp(-((e-14.87)/11.39).^2) + 0.5621*exp(-((e-18.64)/27.74).^2);

% Loop method
Eq2 = zeros(size(e)); 
for i = 1:numel(e)
    Eq2(i) = 0.4075*exp(-((e(i)-14.87)/11.39).^2) + 0.5621*exp(-((e(i)-18.64)/27.74).^2);
end

% Are they equal?
isequal(Eq,Eq2)  % = 1;  yes

[engineer]

it worked, thank you very much.

[engineer]

I have one more question. my matrix 'e' is not in the x axis. It is actually in the y axis. How can I implement my matrix in y axis and find the corresponding X axis and save it as a matrix?

[Adam Danz]

I'm sorry, I don't follow the question. What do you mean by x axis and y axis?

[engineer]

matrix 'e' is output for the function. Therefore, I would like to find the input matrix.

For example:

a = [2;5;7]

a(i) = 2x+5

in this case the answer :

x =[9;15;19]

I hope it is clearer now.

[Adam Danz]

But 'e' is an input variable in your example. Eq is the output.

Do you mean you're trying to solve for this:

e = 0.4075*exp(-((x-14.87)/11.39).^2) + 0.5621*exp(-((x-18.64)/27.74).^2);

where x is unknow and e is known?

[engineer]

yes, exactly.

[engineer]

any suggestion? , I got really stucked here?

[Adam Danz]

Try this out

syms x 
for i = 1:numel(e)
    sol(i) = solve(0.4075*exp(-((x-14.87)/11.39).^2) + 0.5621*exp(-((x-18.64)/27.74).^2) == e(i));
end

[engineer]

I received this error.

Warning: Unable to find explicit solution. For options, see help. 
> In solve (line 317) 
Subscripted assignment dimension mismatch.
Error in sym/privsubsasgn (line 1107)
                L_tilde2 = builtin('subsasgn',L_tilde,struct('type','()','subs',{varargin}),R_tilde);
Error in sym/subsasgn (line 944)
            C = privsubsasgn(L,R,inds{:}); 

[engineer]

Besides, how do you save the each x variable within loop in the code you provided?

[Adam Danz]

sol(i) is the x values that satisfy the function. If you search for that warning within this forum you get lot's of feedback.