matlab中 median函数 实现的程序代码是什么？

首先将数组排序

如果元素数量是奇数，取最中间那个元素；

如果元素数量是偶数，取最中间两个元素的算术平均值。

>>edit median

function y = median(x,dim)

%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]

%

% Class support for input X:

% float: double, single

%

% See also MEAN, STD, MIN, MAX, VAR, COV, MODE.

% Copyright 1984-2005 The MathWorks, Inc.

% $Revision: 5.15.4.6 $ $Date: 2005/05/31 16:30:47 $

% Calculation method for even lists: b - (b-a)/2.

% This method reduces the likelihood of rounding errors.

nInputs = nargin

if isempty(x)

if nInputs == 1

% The output size for [] is a special case when DIM is not given.

if isequal(x,[]), y = nan(1,class(x))returnend

% Determine first nonsingleton dimension

dim = find(size(x)~=1,1)

end

s = size(x)

if dim <= length(s)

s(dim) = 1 % Set size to 1 along dimension

end

y = nan(s,class(x))

elseif nInputs == 1 &&isvector(x)

% If input is a vector, calculate single value of output.

x = sort(x)

nCompare = numel(x)

half = floor(nCompare/2)

y = x(half+1)

if 2*half == nCompare% Average if even number of elements

y = meanof(x(half),y)

end

if isnan(x(nCompare))% Check last index for NaN

y = nan(class(x))

end

else

if nInputs == 1 % Determine first nonsingleton dimension

dim = find(size(x)~=1,1)

end

s = size(x)

if dim >length(s) % If dimension is too high, just return input.

y = x

return

end

% Sort along given dimension

x = sort(x,dim)

nCompare = s(dim) % Number of elements used to generate a median

half = floor(nCompare/2) % Midway point, used for median calculation

if dim == 1

% If calculating along columns, use vectorized method with column

% indexing. Reshape at end to appropriate dimension.

y = x(half+1,:)

if 2*half == nCompare

y = meanof(x(half,:),y)

end

y(isnan(x(nCompare,:))) = NaN % Check last index for NaN

elseif dim == 2 &&length(s) == 2

% If calculating along rows, use vectorized method only when possible.

% This requires the input to be 2-dimensional. Reshape at end.

y = x(:,half+1)

if 2*half == nCompare

y = meanof(x(:,half),y)

end

y(isnan(x(:,nCompare))) = NaN % Check last index for NaN

else

% In all other cases, use linear indexing to determine exact location

% of medians. Use linear indices to extract medians, then reshape at

% end to appropriate size.

cumSize = cumprod(s)

total = cumSize(end) % Equivalent to NUMEL(x)

numMedians = total / nCompare

numConseq = cumSize(dim - 1) % Number of consecutive indices

increment = cumSize(dim) % Gap between runs of indices

ixMedians = 1

y = repmat(x(1),numMedians,1) % Preallocate appropriate type

% Nested FOR loop tracks down medians by their indices.

for seqIndex = 1:increment:total

for consIndex = half*numConseq:(half+1)*numConseq-1

absIndex = seqIndex + consIndex

y(ixMedians) = x(absIndex)

ixMedians = ixMedians + 1

end

end

% Average in second value if n is even

if 2*half == nCompare

ixMedians = 1

for seqIndex = 1:increment:total

for consIndex = (half-1)*numConseq:half*numConseq-1

absIndex = seqIndex + consIndex

y(ixMedians) = meanof(x(absIndex),y(ixMedians))

ixMedians = ixMedians + 1

end

end

end

% Check last indices for NaN

ixMedians = 1

for seqIndex = 1:increment:total

for consIndex = (nCompare-1)*numConseq:nCompare*numConseq-1

absIndex = seqIndex + consIndex

if isnan(x(absIndex))

y(ixMedians) = NaN

end

ixMedians = ixMedians + 1

end

end

end

% Now reshape output.

s(dim) = 1

y = reshape(y,s)

end

%============================

function c = meanof(a,b)

% MEANOF the mean of A and B with B >A

%MEANOF calculates the mean of A and B. It uses different formula

%in order to avoid overflow in floating point arithmetic.

c = a + (b-a)/2

k = (sign(a) ~= sign(b)) | isinf(a) | isinf(b)

c(k) = (a(k)+b(k))/2

1、matlab是一个功能强大的软件，不仅仅在数据处理方面很优秀，在界面编程方面同样优秀，这里简单介绍下matlab界面编程的基础步骤。

2、在打开的matlab程序中，点击new---graphic user interface，打开创建gui向导--我们选择blank gui，创建空白的gui界面---选择左侧我们需要的控件，如下图，我们选择一个button---将控件拖入到gui界面的合适的位置，双击打开设置属性的界面---设计好界面后，我们先不要编写函数内容，先运行界面---他会提醒我们激活界面将保存界面和代码，我们选择yes---输入文件名，点击保存---我们回到界面编辑界面，点击button右键打开右键菜单，点击view callbacks---callback，来跳转到该控件的回调函数---我们在该函数中输入代码---这时，我们运行程序，点击按钮，即可以在命令窗口中看到button执行的效果。

3、先运行界面，使得matlab给我们创建界面的代码，然后在view callback。

一般的的查询可在matlab里的帮助界面进行搜索，点击帮助。

打开帮助页面，左侧检索栏进行检索需要查询的语句，然后即可查看右侧查询结果。

或者在主界面，输入help 空格+你要查询的内容，进行查询。下次你可以尝试一下。

一般程序都会有不懂得语句，或没用过的，可以在刚刚说过的帮助页面进行查询，看如何使用，输入参量什么意义，程序输出结果是什么。

你这个描述太过于简略了，我只能给出这样的答案了，一般可以都给一点程序，也许会有对答题人帮助。

不过你这个程序的确有点复杂，不根据前后逻辑，和主程序和目的是很难解答的。

你可以看看主程序，再查查帮助。

希望对你有所帮助。谢谢。

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