MATLAB，使用if语句比较阵列 [英] Matlab, comparing array using if statement

问题描述

我已搜查了净试图找到一个答案，这个问题我有。

I have searched the net trying to find an answer to this problem I have.

我有一个数组很像以下

A = [2 4 6 8 ; 3 5 7 9 ; 1 4 6 9]

row median = [ 5 6 5 ]
col median = [ 2 4 6 9 ]

从这些数值我想创建一个中间的地图。所以我创建数组

From these values I want to create a median map. So I have created the array

MedianMap = int8(zeros(MAX_ROWS, MAX_COLS))

在这阵我要分配三个不同的值：1，0，-1。这样的中位图输出将阵列的A的大小相同：

Within this array I want to assign three different values: 1, 0, -1. So the median map output will be of the same size of array 'A':

• 如果该值大于两行和列中值较大的一个1被分配给该位映射


• 如果该值小于两行和列中值-1被分配给该位映射


• ，否则为0？

我怎么能每行每列遍历了A数组中，它涉及到其各自的列和行中位数？

How can I traverse through every row and column in the "A" array and relate it to its respective column and row median?

我已经写在C code中的code，它是SUCESSFUL，但只是在Matlab中挣扎。

I have written the code in C code and it was sucessful, however just struggling in Matlab.

推荐答案

下面是我会怎么做：

MedianMap = ...
    ( bsxfun(@gt,A,col_median) & bsxfun(@gt,A,row_median.') ) - ...
    ( bsxfun(@lt,A,col_median) & bsxfun(@lt,A,row_median.') );

这一个是多线程（适用于更大的问题），并没有任何涉及其他答案（更小的峰值内存占用）的临时的。

This one is multi-threaded (suited for much larger problems) and doesn't have any of the temporaries involved in the other answers (much smaller peak memory footprint).

这不是很pretty虽然:)所以，如果有更好的可读性是你以后，使用 meshgrid 在BrianL的回答，或 repmat ：

It's not very pretty though :) So if better readability is what you're after, use either meshgrid as in BrianL's answer, or repmat:

Col_median = repmat(col_median, size(A,1),1);
Row_median = repmat(row_median.', 1, size(A,2));

MedianMap = ...
    ( A > Col_median & A > Row_median ) - ... 
    ( A < Col_median & A < Row_median ); 

或由那些矩阵为RASMAN做乘法：

or multiplication by a ones-matrix as Rasman did:

Col_median = ones(size(A,1),1) * col_median;
Row_median = row_median.' * ones(1,size(A,2));

MedianMap = ...
    ( A > Col_median & A > Row_median ) - ... 
    ( A < Col_median & A < Row_median ); 

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