how to enter frequency type data in R with class intervals

Dear all,

Given data of a continuous frequency distribution with class  
intervals ..
how to enter such data so that we can use the normal mean, median  
and mode
functions to calculate them and also can draw histogram ..

for example how to enter this data in R

 Height range[image:
?]<http://en.wikipedia.org/wiki/Frequency_distribution#> Number
of students[image: ?]
<http://en.wikipedia.org/wiki/Frequency_distribution#> Cumulative
number[image: ?] <http://en.wikipedia.org/wiki/ 
Frequency_distribution#> 4.5?5.0
feet 25 25 5.0?5.5 feet 35 60 5.5?6 feet 20 80 6.0?6.5 feet 20  
100

The textConnection function allows you to simulate file input from  
material cut and pasted from text sources:

 > dtabl <- read.table(textConnection("4.5?5.0 feet 25 25 \n5.0?5.5  
feet 35 60 \n5.5?6 feet 20 80 \n6.0?6.5 feet 20 100"),  
header=FALSE, stringsAsFactors=FALSE)
 > names(dtabl) <- c("Interval", "units", "Freq", "Cum_Freq")
 > dtabl
   Interval units Freq Cum_Freq
1  4.5?5.0  feet   25       25
2  5.0?5.5  feet   35       60
3    5.5?6  feet   20       80
4  6.0?6.5  feet   20      100

You may need to remove extraneous linefeeds inserted by our mail  
clients.

David Winsemius, MD
West Hartford, CT