在MATLAB中使用If语句可能的向量化 [英] Possible Vectorization using If Statements in MATLAB

问题描述

假设我具有以下列向量

res1 = -0.81              res2 =  0.61
        0.1                      -0.4
       -0.91                      0.62
        0.2                      -0.56
        0.63                     -0.72

，我有两个固定常数D = 0.5.现在假设res1的元素称为X，而res2的元素称为Y.我有以下条件

and I have two fixed constant D = 0.5. Now suppose an element of res1 is called X and an element of res2 is called Y. I have the following conditions

if (X > D && Y < -D)
     output = 1
elseif (X < -D && Y > D)
     output = -1
else
     output = 0
end

我的问题是这个

是否可以将这些条件向量化"以遍历整个向量res1和res2，这样我的输出向量就可以给出(例如):

Is it possible to "vectorize" these conditions to iterate over the entire vectors res1 and res2, such that my output vector would give (for example) :

 output = -1
           0
          -1
           0
           1

?

我知道我可以通过循环来做到这一点，但是我宁愿避免这样做，因为这些向量实际上很大(> 10000).我曾尝试使用逻辑索引，但无济于事(除非我实施错误).

I know I can do it via a loop, but I would prefer to avoid it since these vectors are actually quite large (>10000). I have attempted to use logical indexing, but to no avail (unless I'm implementing it wrong).

任何帮助将不胜感激！

推荐答案

您可以使用

You can use logical arrays to replace the conditional statements and scale them with appropriate scaling factors for the final output -

%// Logical arrays corresponding to the IF and ELSEIF conditional statements
case1 = res1>D & res2<-D
case2 = res1<-D & res2>D

%// Get the final output after multiplying each case with the
%// scaling factors 1 and -1 respectively. 
%// The default value of `zero` for the ELSE part is automatically taken 
%// care of because we are using logical array of ones and zeros anyway
output = case1 + -1*case2 %// or simply case1 - case2

---

样品运行-

---

Sample run -

>> res1
res1 =
   -0.8100
    0.1000
   -0.9100
    0.2000
    0.6300
>> res2
res2 =
    0.6100
   -0.4000
    0.6200
   -0.5600
   -0.7200
>> output
output =
    -1
     0
    -1
     0
     1

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