R绘图与颜色渐变

Question

下面是使用R函数persp3d并指定颜色的3D曲线.

library(rgl)

y = seq(-5,25,by=0.1)
x = seq(5,20,by=0.2)

NAs <- rep(NA, length(x)*length(y))
z <- matrix(NAs, length(x), byrow = T)
for(i in seq(1,length(x))) {
    for(j in seq(1,length(y))) {
        val = x[i] * y[j]
        z[i,j] = val
        if(z[i,j] < 0.02) {
            z[i,j] = NA
        }

    }
}

col <- rainbow(length(x))[rank(x)]

open3d()
persp3d(x,y,z,color=col,xlim=c(5,20),ylim=c(5,10),axes=T,box=F,xlab="X Axis",ylab="Y Axis",zlab="Z Axis")

它产生这个图像:

在当前版本中,对于x值为15,无论z值如何,颜色都是蓝色.但我喜欢这样,高z值是深蓝色而低z值是浅蓝色,如果这是有道理的.我该怎么做这样的事情,这样颜色不仅可以区分x值,还可以区分z值？

Answer 1

您必须使用HSV格式的颜色而不是RGB格式.我觉得这样比较容易.

请参阅下面的示例代码.

library(rgl)

y = seq(-5,25,by=0.1)
x = seq(5,20,by=0.2)

NAs <- rep(NA, length(x)*length(y))
z <- matrix(NAs, length(x), byrow = T)
for(i in seq(1,length(x))) {
  for(j in seq(1,length(y))) {
    val = x[i] * y[j]
    z[i,j] = val
    if(z[i,j] < 0.02) {
      z[i,j] = NA
    }

  }
}

为x的每个值创建唯一的颜色.

col <- rainbow(length(x))[rank(x)]

通过重复col length(y)次数创建颜色网格

col2 <- matrix(rep(col,length(y)), length(x))
for(k in 1:nrow(z)) {

  row <- z[k,]
  rowCol <- col2[k,]  
  rowRGB <- col2rgb(rowCol) #convert hex colors to RGB values
  rowHSV <- rgb2hsv(rowRGB) #convert RGB values to HSV values

  row[is.na(row)] <- 0
  v <- scale(row,center=min(row), scale=max(row)-min(row)) # scale z values to 0-1

  rowHSV['s',] <- v #update s or v values by our scaled values above
  # rowHSV['v',] <- v  # try changing either saturation or value i.e. either s or v

  newRowCol <- hsv(rowHSV['h',], rowHSV['s',], rowHSV['v', ]) #convert back to hex color codes
  col2[k,] <- newRowCol #Replace back in original color grid
}

open3d()
persp3d(x,y,z,color=col2,xlim=c(5,20),ylim=c(5,10),axes=T,box=F,xlab="X Axis",ylab="Y Axis",zlab="Z Axis")

这应该给予以下.您可以围绕饱和度或颜色值进行缩放,以获得所需的"亮度"或"黑暗"色调.