r - 如何结合情节和传说？

Question

我正在尝试将图例附加到 R 中的情节。 我尝试了以下代码(取自 http://www.harding.edu/fmccown/r/)

# Define cars vector with 5 values
cars <- c(1, 3, 6, 4, 9)

# Define some colors ideal for black & white print
colors <- c("white","grey70","grey90","grey50","black")

# Calculate the percentage for each day, rounded to one 
# decimal place
car_labels <- round(cars/sum(cars) * 100, 1)

# Concatenate a '%' char after each value
car_labels <- paste(car_labels, "%", sep="")

# Create a pie chart with defined heading and custom colors
# and labels
pie(cars, main="Cars", col=colors, labels=car_labels,
   cex=0.8)

# Create a legend at the right   
legend(1.5, 0.5, c("Mon","Tue","Wed","Thu","Fri"), cex=0.8, 
   fill=colors)

然而，这并不能很好地工作。在 pie(cars, main="Cars", col=colors, labels=car_labels,cex=0.8) 行之后，显示的图没有图例:-) ......我在网上看到的每一个例子好像在plotting函数之后都有legend函数所以看起来很奇怪......

当我尝试执行我得到的图例函数时

legend(1.5, 0.5, c("Mon","Tue","Wed","Thu","Fri"), cex=0.8, + fill=colors) Error in strwidth(legend, units = "user", cex = cex) : plot.new has not been called yet

Answer 1

你离开了坐标系。试试这个吧

# Create a legend at the right   
legend("topleft", c("Mon","Tue","Wed","Thu","Fri"), cex=0.8, fill=colors)

生成下面的图表:

有关不同的放置选项，请参阅图例 的帮助页面。