eval

ExecuteMATLABexpression in text

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Syntax

eval(expression) [output1,...,outputN] = eval(expression)

Description

eval(expression)evaluates the MATLAB^®code represented byexpression. If you useevalwithin an anonymous function, nested function, or function that contains a nested function, the evaluatedexpressioncannot create a variable.

[output1,...,outputN] = eval(expression)stores output fromexpressionin the specified variables.

Input Arguments

expression

Character vector or string scalar that contains a valid MATLAB expression.

To include a numeric value in the expression, convert it to a character vector or string scalar.

Output Arguments

output1,...,outputN

Outputs from the evaluatedexpression.

Examples

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Variable Name Evaluation

Select a matrix to plot at runtime.

This example requires that you have a matrix in the current workspace. For example:

aMatrix = magic(5);

Interactively request the name of a matrix to plot, and callevalto use its value.

expression = input('Enter the name of a matrix: ','s');if(exist(expression,'var')) mesh(eval(expression))end

If you typeaMatrixat the input prompt, this code creates a mesh plot ofmagic(5).

Tips

Many common uses of theevalfunction are less efficient and are more difficult to read and debug than other MATLAB functions and language constructs. For more information, see替代eval函数.
Whenever possible, do not include output arguments within the input to theevalfunction, such aseval(['output = ',expression]). The preferred syntax,
```
output = eval(expression)
```
allows the MATLAB parser to perform stricter checks on your code, preventing untrapped errors and other unexpected behavior.