Question

matlab 自定义函数问题

function whatiwant=findsth(a,x)
[n,m]=size(a);
b=zeros(1,n*m);
k=1;
for i=1:1:n;
for j=1:1:m;
b(1,k)=a(i,j);
k=k+1;
end;
end;
c=sort(b);
whatiwant=(c(1,n*m/2)+c(1,n*m/2+1))/2;

我想的是这样的，自定义一个函数，传a矩阵进去，然后求出中位数
可是提示[n,m]=size(a);这一步有错，请问该怎么改？
或者，这一段有什么更优化的办法？
其实不只是中位数，也许是50%的，也许是30%，那个x就是干这个事的。
怎么传矩阵呢？

Answer 1

matlab自带了中位数的函数median
如果要求2维矩阵，可以先加一个
b=a(:);

>> help median

MEDIAN Median value.
For vectors, MEDIAN(X) is the median value of the elements in X.
For matrices, MEDIAN(X) is a row vector containing the median
value of each column. For N-D arrays, MEDIAN(X) is the median
value of the elements along the first non-singleton dimension
of X.

MEDIAN(X,DIM) takes the median along the dimension DIM of X.

Example: If X = [0 1 2
3 4 5]

then median(X,1) is [1.5 2.5 3.5] and median(X,2) is [1
4]

See also MEAN, STD, MIN, MAX, COV.

Answer 2

怎么可能报错？

a =

2 3
6 8

>> findsth(a,2)

ans =

4.5000

>> [n m] =size(a)

n =

2

m =

2

文件保存名与函数名一致的问题吧，还有工作路径，低级问题。