R图像（）绘制矩阵旋转？ [英] R image() plots matrix rotated?

问题描述

我一直在阅读

如何使布局相同作为印刷矩阵？这不仅仅是让转置翻转x和y，因为它会以倒置图像结束。

解决方案

你可以反转矩阵，然后转置。

  mat1<  -  apply（mat1,2，rev）
图像（1：3,1：3，t（mat1））
  

因为它绘制而令人困惑从下到上按行排列，但R按列向下索引矩阵。因此，第一行中从左到右的像素对应于矩阵中的第一列，自上而下。

I've been reading the docs for R image() but I don't get it. Why does this matrix:

> mat1
     [,1] [,2] [,3]
[1,]    1    0    1
[2,]    0    1    0
[3,]    0    0    0

Plotted like this:

> image(c(1:3), c(1:3), mat1)

yield this:

And how can I make the layout the same as the printed matrix? It's not a matter of just taking the transpose to flip x and y, as that ends up with an 'upside down' image.

解决方案

You could reverse the matrix, then transpose.

mat1 <- apply(mat1, 2, rev)
image(1:3, 1:3, t(mat1))

It's confusing because it draws by row from bottom up, but R indexes matrices by column, top down. So, the pixels in the first row, from left to right, correspond to the first column in the matrix, top down.

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