how to plot a fitted smooth line on histograms?

for example,
x <- read.table(....);  here x is a vector containing  my data to be analyzed.
hist(x,plot=TRUE,breaks=200)
then I got a histogram graph. However, How can't get a smooth curve
based on the histogram cells to show out the outline?

Thanks very much.
You may check the chapter 8 Probability distributions in An Introduction to R.

Wuming
for example,
x <- read.table(....);  here x is a vector containing  my data to be analyzed.
hist(x,plot=TRUE,breaks=200)
then I got a histogram graph. However, How can't get a smooth curve
based on the histogram cells to show out the outline?

Thanks very much.

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