R高度图-相对于出生日期

# Get all the files ending with .heights
filelist <- list.files(pattern = "\\.heights")

# Get all the data. Put into a single data.frame
# Assuming that you don't have thousands of
# files/measurements, rbind()ing shouldn't be too slow. 
df <- data.frame(person = character(),
                 dates = character(),
                 height = numeric())

# Iterate through, collecting the data into a data.frame
for (fname in filelist){
  x <- read.table(fname, sep="", as.is = TRUE)
  person <- gsub("\\.heights", "", fname)
  names(x) <- c("dates", "height")
  df <- rbind(df, data.frame(person = rep(person, times = nrow(x)),
                             dates = x$dates, 
                             height = x$height))
}

# Convert dates to POSIXct
df$dates <- strptime(as.character(df$dates), "%d/%m/%Y")
df$dates <- as.POSIXct(df$dates)

# Plot with qplot
require(ggplot2)
pdf("Heights.pdf")
qplot(dates, height, data = df, color = person)
dev.off()

# Plot with base graphics
pdf("Heights_2.pdf")
plot(df$dates, df$height, col = as.numeric(df$person))
dev.off()