如何为2个绘制的条创建1个x轴标签

Question

I've created a bar plot but need to change the x-axis labels so that there's one label for the first two bars and a second label for the next two bars. At present each of the 4 plotted bars are individually labelled, but each label is repeated twice. Sorry if the terminology isn't correct, I'm new to this whole R thing.

The code I've entered is:

attach(flydiets)
y <- matrix(protein,nrow = 100, ncol = 4, byrow = FALSE)
y[ , c(1,2,3,4)] <- y[ , c(1,3,2,4)]
means <- apply(y,2,mean)
tags = c("25°", "25°","28°", "28°")
barx <- barplot(means, beside=TRUE,col=c("white","grey"), 
ylim=c(0,600),  names.arg=tags, axis.lty=1, xlab="Temperature (°C)",
ylab="Protein Consumed (µg)")
sd <- apply(y,2,sd)## calculate a standard deviation for each column of y
sd <- matrix(sd,2,2) ## arrange them as a 2 x 2 matrix
se <- sd/sqrt(100)  ## convert them to standard errors
arrows(barx,means+1.96*se, barx, means-1.96*se, angle=90, code=3, length=0.1) 
legend("topright", legend=c("Male", "Female"), fill=c("white", "grey"), cex=0.8)

Any help would be appreciated. Cheers

Answer 1

Below is a reduced sample of data set from the original.

"sex","temp","carbohydrate","protein"

"M","25", 396.075, 358.28

"M","25", 252.70, 204.70

"M","25", 441.81, 461.86

"M","25", 430.88, 374.67

"M","25", 520.46, 439.10

"M","25", 484.45, 561.66

"M","28", 590.17, 429.98

"M","28", 383.23, 517.82

"M","28", 431.945, 289.22

"M","28", 410.61, 530.89

"M","28", 622.14, 533.25

"M","28", 509.58, 425.89

"F","25", 489.68, 209.87

"F","25", 451.03, 34.30

"F","25", 461.01, 283.88

"F","25", 715.74, 506.62

"F","25", 576.33, 476.30

"F","28", 450.12, 452.56

"F","28", 498.53, 376.46

"F","28", 517.02, 303.82

"F","28", 355.84, 78.65

"F","28", 404.07, 229.88

"F","28", 537.57, 253.27

Thanks for your help