Matlab快速入门之调用函数

今天来给各位说下如何在Matlab中调用函数，MATLAB®内置了大量执行计算任务的函数，尤其随着版本的迭代，内置的函数会越来越多。在其他编程语言中，函数等同于子例程或方法。本文，将以几个例子来说明Matlab中调用函数的具体方法，由于不同函数调用方式不同，这里只能作为参考。

要调用函数，例如max，请将其输入参数括在圆括号中：

>> A = [1 3 5];
>> max(A)

ans =

     5

如果存在多个输入参数，请使用逗号加以分隔：

>> B = [3 6 9];
>> union(A,B)

ans =

     1     3     5     6     9

通过将函数赋值给变量，返回该函数的输出：

>> maxA = max(A)

maxA =

     5

如果存在多个输出参数，请将其括在方括号中：这里需要注意，bounds边界函数在Matlab R2021b中引入，之前的版本会报错不存在该函数

[minA,maxA] = bounds(A)

minA = 1
maxA = 5

用引号将任何文本输入括起来：

disp("hello world")

hello world

有关双引号的用法，需要Matlab版本高于R2017a。

要调用不需要任何输入且不会返回任何输出的函数，请只键入函数名称：

clc

clc函数清空命令行窗口。

需要注意的是，当你不了解你想要调用函数的输入参数和输出结果时，可以通过help获取该函数的使用帮助文档。例如：

>> help max
 max    Largest component.
    For vectors, max(X) is the largest element in X. For matrices,
    max(X) is a row vector containing the maximum element from each
    column. For N-D arrays, max(X) operates along the first
    non-singleton dimension.
 
    [Y,I] = max(X) returns the indices of the maximum values in vector I.
    If the values along the first non-singleton dimension contain more
    than one maximal element, the index of the first one is returned.
 
    max(X,Y) returns an array the same size as X and Y with the
    largest elements taken from X or Y. Either one can be a scalar.
 
    [Y,I] = max(X,[],DIM) operates along the dimension DIM. 
 
    When X is complex, the maximum is computed using the magnitude
    max(ABS(X)). In the case of equal magnitude elements, then the phase
    angle max(ANGLE(X)) is used.
 
    max(..., NANFLAG) specifies how NaN (Not-A-Number) values are treated.
    NANFLAG can be:
    'omitnan'    - Ignores all NaN values and returns the maximum of the 
                   non-NaN elements.  If all elements are NaN, then the
                   first one is returned.
    'includenan' - Returns NaN if there is any NaN value.  The index points
                   to the first NaN element.
    Default is 'omitnan'.
 
    Example: If X = [2 8 4; 7 3 9] then 
                max(X,[],1) is [7 8 9],
                max(X,[],2) is [8; 9] and 
                max(X,5)    is [5 8 5; 7 5 9].