How to request input and set as symbols?

Question

David Hagan 2012-2-10

0
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https://ww2.mathworks.cn/matlabcentral/answers/28717-how-to-request-input-and-set-as-symbols

I am attempting to write a code for the Newton-Raphson method which essentially solves a system of n equations and n unknowns. I am trying to ask for user input (in the form of equations, initial values, etc.). As far as I know, I have to set the variables to symbols.

How can I request the user input for the variables to be used before asking for the equations?

in = 1;
data = [];
i = 1;
while in ~= 0
    var_string(i) = input('What variables are you using?  End with "end" ','s');
    if var_string(i) == 'end'
        break;
    else
        variable(i) = sym(var_string(i))
        i = i + 1;
    end
end

This is what I have at this point. Is there a way to do this? Thanks.

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Answer 1

Walter Roberson 2012-2-10

1
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https://ww2.mathworks.cn/matlabcentral/answers/28717-how-to-request-input-and-set-as-symbols#answer_37047

在 MATLAB Online 中打开

input() is going to return a string, not a cell array. Unless the string happens to be only a single character long, it is not going to fit in to var_string(i) . Switch to cell arrays for var_string .

Also, do not use == to compare strings. For example,

'hi' == 'end'

is going to give you an error about inconsistent dimensions. Use one of the string comparison functions.