如何阻止 ggplot2 将矩阵旋转 90 度？

Question

我正在尝试使用 ggplot2 创建热图，但我注意到当我绘制它时它似乎将矩阵向左旋转了 90 度。这很奇怪，使用coord_flip() 和t() 不起作用，因为它们将其旋转到左侧，而不是右侧（因此，它们不是更正，而是创建了一个旋转 180 度的热图）。是否有任何选项或技巧可以防止这种情况发生？以下是相关代码：

#this is needed to run custHeat
zeroInterval <- function(mat, colors){
  #modified version of findInterval such that zero is given its own category
  #This function takes intervals as left exclusive, right inclusive.
  #This is mostly so that intervals consisting of a single value will still be represented.
  intervalMat <- matrix(0, nrow=nrow(mat), ncol=ncol(mat))
  j <- 1
  for(i in 1:(length(colors) - 1)){
    if(colors[i] != colors[i+1]){
      intervalMat[mat>colors[i] & mat<=colors[i+1]] <- j
      j <- j + 1
    } else {
      intervalMat[mat==colors[i]] <- j
      j <- j + 1
    }
  }
  return(intervalMat)
}

#this actually plots the heatmap
custHeat <- function(M){

  #create color bins/ranges for skewed matrix
  color_bins <- c(-5, -4, -3, -2, -1, 0, 0, 1)
  colors <- c('#67001F', '#B2182B', '#D6604D', '#F4A582', '#FDDBC7', "#FFFFFF", '#C6DBEF')

  #create complete color palette
  color_palette <- colorRampPalette(colors)(length(color_bins) - 1)

  #This function assigns a number to each matrix value, so that it is colored correctly
  mod_mat <- zeroInterval(random_matrix, color_bins)


  ## remove background and axis from plot
  theme_change <- theme(
    plot.background = element_blank(),
    panel.grid.minor = element_blank(),
    panel.grid.major = element_blank(),
    panel.background = element_blank(),
    panel.border = element_blank(),
    axis.line = element_blank(),
    axis.ticks = element_blank(),
    axis.text.x = element_blank(),
    axis.text.y = element_blank(),
    axis.title.x = element_blank(),
    axis.title.y = element_blank()
  )

  ## output the graphics
  ggplot(melt(mod_mat), aes(x = X1, y = X2, fill = factor(value))) +
    geom_tile(color = "black") +
    scale_fill_manual(values = color_palette, name = "") +
    theme_change
}

##create random matrix, skewed toward negative values
random_matrix <- matrix(runif(100, min = -5, max = 1), nrow = 10)
random_matrix[1,] <- 0 #zeros should be at the top row of the heatmap
custHeat(random_matrix)

Answer 1

您可以通过将矩阵在另一个方向预旋转 90 度来抵消绘图功能的 90 度逆时针旋转：

## An example matrix
(m <- matrix(1:9, ncol=3))
#      [,1] [,2] [,3]
# [1,]    1    4    7
# [2,]    2    5    8
# [3,]    3    6    9

## The same matrix rotated 90 degrees clockwise
t(m)[,nrow(m):1]
#      [,1] [,2] [,3]
# [1,]    3    2    1
# [2,]    6    5    4
# [3,]    9    8    7

---

稍后添加：

一些 R 绘图函数使用与 image() 相同的约定，而其他的则不使用。 （请随时添加到此列表中。）

m <- matrix(1:9, ncol=3)


## ------- These plotting functions DO rotate a matrix --------

## image()
image(m, col=blues9)

## levelplot() -- a lattice equivalent of image()
library(lattice)    
levelplot(m, at=(1:10)-0.5, col.regions=blues9)

## Others
contour(m)
filled.contour(m, color=colorRampPalette(blues9))
persp(m) 
lattice::contourplot(m)
lattice::wireframe(m)  ## Nicely illustrates the logic of the indexing it uses


## ------- These plotting functions DO NOT --------

## imageRaster() -- a graphical primitive used by image(), among other functions 
plot(0:1, 0:1, type="n", xlab="", ylab="")
rasterImage(matrix(blues9, ncol=3), 0,0,1,1, interpolate=FALSE)

## grid.raster() -- imageRaster()'s counterpart in the grid graphical system
library(grid)
grid.raster(matrix(blues9, ncol=3), interpolate=FALSE)

## plot(raster()) in raster package
library(raster)
plot(raster(m), col=blues9)