r的行为奇怪地将特征向量复制到i循环中的矩阵
我有点困惑。一个矩阵A具有8个特征值，其中有些是复杂的，有些是真实的。我想仅将与真实特征值相对应的特征向量复制为矩阵M，否则应用0填充列。我使用该代码：
M <- matrix(,ncol=8,nrow=8)
for(i in 1:8) {
M[,i] <- ifelse(Im(eigen(A)$val[i]) == 0, eigen(A)$vec[,i], 0)
}
但是结果好像我执行了此：（
M <- matrix(,ncol=8,nrow=8)
for(i in 1:8) {
M[,i] <- ifelse(Im(eigen(A)$val[i]) == 0, eigen(A)$vec[**1**,i], 0)
}
契约中的BTW生成的输出与上面的代码完全相同）。我的误解在哪里？
I'm a bit confused. A matrix A has 8 eigenvalues, some of them are complex, some are real. I want to copy only the eigenvectors that correspond to the real eigenvalues as columns into a Matrix M, otherwise the column should be filled with 0s. I use the code:
M <- matrix(,ncol=8,nrow=8)
for(i in 1:8) {
M[,i] <- ifelse(Im(eigen(A)$val[i]) == 0, eigen(A)$vec[,i], 0)
}
but the result is as if I executed this one:
M <- matrix(,ncol=8,nrow=8)
for(i in 1:8) {
M[,i] <- ifelse(Im(eigen(A)$val[i]) == 0, eigen(A)$vec[**1**,i], 0)
}
(that BTW in deed generates exactly the same output as the code above). Where is my misconception?
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I found the solution through the [email protected]: it's not a matter of matrix or for i loop behavior, it's a matter of ifelse that behaves in R very different to e.g ifelse in C. So the correct way to process my idea is: