在 R 中繪製不同顏色的圖例項
本文將演示如何在 R 中繪製不同顏色的圖例項。
在 R 中使用 legend 函式為繪圖新增圖例
legend 函式用於在圖上繪製圖例物件。它需要 x 和 y 座標作為前兩個引數來指定圖例的位置。雖然可以使用諸如"left"、"bottomright"等關鍵字來指定它。下一個引數稱為 legend，它表示為需要在圖例中顯示的字元向量。在這種情況下，我們繪製由三角形或圓形表示的線和點。線和點有不同的顏色，它們需要相應地顯示在圖例中。以下程式碼片段僅在圖例中繪製形狀和文字。
library(ggplot2)
plot( 0, type = "n", xlim = c(0,5), ylim = c(0,5) )
A <- matrix( c( c(4,1,3,2), c(1,3,4,4)), ncol = 2 )
B <- matrix( c( c(1,4,3,2), c(1,3,1,1)), ncol = 2 )
lines( A, col = "brown" )
points( A, col = "blue", pch = 17 )
lines( B, col = "cyan" )
points( B, col = "purple", pch = 19 )
legend( x = "topleft",
legend = c("Brown line, blue triangles","Cyan line, purple points"),
col = c("blue","purple"), lwd = 2, lty = c(0,0),
pch = c(17,19) )
我們還可以通過增加 lty 引數向量的值來新增行。請注意，那些對應於直線和不間斷的線。另一方面，pch 參數列示對映到 0:25 整數值的繪圖符號，並在 points 函式文件中進行了描述。
library(ggplot2)
plot( 0, type = "n", xlim = c(0,5), ylim = c(0,5) )
A <- matrix( c( c(4,1,3,2), c(1,3,4,4)), ncol = 2 )
B <- matrix( c( c(1,4,3,2), c(1,3,1,1)), ncol = 2 )
lines( A, col = "brown" )
points( A, col = "blue", pch = 17 )
lines( B, col = "cyan" )
points( B, col = "purple", pch = 19 )
legend( x = "topleft",
legend = c("Brown line, blue triangles","Cyan line, purple points"),
col = c("brown","cyan"), lwd = 1, lty = c(1,1),
pch = c(17,19), merge = FALSE)
使用雙 legend 呼叫繪製不同顏色的圖例項
上一個示例顯示具有相同顏色的單個專案的線條和形狀。這可以通過 legend 函式的兩次呼叫來解決，每個函式都用不同的顏色分別顯示線條和形狀。不過請注意，其中一個呼叫的 legend 引數應該具有空向量值。
library(ggplot2)
plot( 0, type = "n", xlim = c(0,5), ylim = c(0,5) )
A <- matrix( c( c(4,1,3,2), c(1,3,4,4)), ncol = 2 )
B <- matrix( c( c(1,4,3,2), c(1,3,1,1)), ncol = 2 )
lines( A, col = "brown" )
points( A, col = "blue", pch = 17 )
lines( B, col = "cyan" )
points( B, col = "purple", pch = 19 )
legend( x = "topleft",
legend = c("Brown line, blue triangles","Cyan line, purple points"),
col = c("brown","cyan"), lwd = 1, lty = c(1,1),
pch = c(NA,NA) )
legend( x = "topleft",
legend = c("",""),
col = c("blue","purple"), lwd = 1, lty = c(0,0),
pch = c(17,19), bty= 'n')
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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