Convert a string into mathematical function of x :f(x)? [closed]

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Closed 5 years ago.

Hello I'm a beginner in Android programming. I'm working on a graphic calculator but i still have the problem of converting the function to math

For example :

y=cos(x^2)-ln(x)

should look like

y=Math.cos(x*x) - Math.log(x)

And than we plot it.

Thank You

回答1:

I assume you want to convert a String to a float or double?

String input = "3.14";
float x = Float.parseFloat(input);

This code converts the String "3.14" into a float. You can use this float in the function you described in the question.

EDIT: If you want to convert the full function String into Java code, you should limit the input to buttons. For example, add a button named "Cos", and remember in the code the user wants to use the Cosinus function. Then the user enters a value, and presses "Enter". The code knows it should use the cosinus function, and x is the value entered in an EditText. That value should be parsed using Float.parseFloat().

来源：https://stackoverflow.com/questions/21137526/convert-a-string-into-mathematical-function-of-x-fx