Using relational operator as a function input

Question

Andrew Yoon 2019-3-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/447984-using-relational-operator-as-a-function-input

回答： Walter Roberson 2019-3-7

I do not know how to use relational operator as a function input.

For example, if I have to creat a function that recieves a condition like below, in which data represents a matrix of numbers

count_var(data < 0.2)

I don't know exactly how to pass down the relational operator < or any operators that will be passed down by the user

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Answer 1

Sreelakshmi S.B 2019-3-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/447984-using-relational-operator-as-a-function-input#answer_364261

If it’s the condition you want to pass, you could always pass it as a string or a character array and then parse it to get the relational operator.

You can also use function handles for this purpose by placing the condition you wish to pass inside a function.

For eg: if the condition you want to check is if a variable you pass is less than 3:

Define a function that checks this condition:

function out=condition_check(value)
%function to verify a condition(here to check if the passed value is less than 3)
out=0;
if(value<3)
    out=1;
end
end

Now modify your function such that it takes a function handle as an input:

function your_function(condition,x)%condition is a function handle
%a trial function that prints yes if x satisfies the condition in the function pointed to by the 'condition' function handle and no if it doesn't 
if(condition(x))
    disp("yes");
else
    disp("No");
end 
end

Now you can call the function as follows:

your_function(@condition_check,10);%% replace 10 with your data point and @condition_check with the handle to whatever function contains the condition you want to check