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From |
Richard Fox <r.p.fox@bham.ac.uk> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
st: rounding error |

Date |
Tue, 20 Dec 2011 13:57:03 +0000 |

Dear statalist, I have written a program that summarises a continuous variable by a categorical variable and over a discrete time period, say Weight at a series of GP visits. The results are generally as expected but sometimes the rounding does not seem to work. I capture the information I need as in the following example (this is just a small extract from the program, obviously there are argument definitions and tabulations etc.); local acc = .1 qui su `x' if New`v' == Tnam[`i',1] & New`w'==Wnam`i'[`j',1],d local Median_`i'_`j' = round(r(p50),`acc') The results I obtain (see 2 examples below) often have values that have many decimal places which appears to suggest that the rounding is not working. However if I run a basic summary of the particular variable the results I get do not have the numerous decimal places so I'm not sure if the issue is with the rounding statement. Any ideas? local acc = .1 . su Weight if Trt==1 & Week==3, d My program in this case returns a value of 84.30000000000001 Weight ------------------------------------------------------------- Percentiles Smallest 1% 75.6 75.6 5% 75.6 93.1 10% 75.6 . Obs 2 25% 75.6 . Sum of Wgt. 2 50% 84.35 Mean 84.35 Largest Std. Dev. 12.37437 75% 93.1 . 90% 93.1 . Variance 153.125 95% 93.1 75.6 Skewness 0 99% 93.1 93.1 Kurtosis 1 . local x= r(p50) . di `x' 84.35 . local y= round(r(p50),`acc') . di `y' 84.3 . . . su Weight if Trt==2 & Week==1, d My program in this case returns a value of 79.80000000000001 Weight ------------------------------------------------------------- Percentiles Smallest 1% 67.7 67.7 5% 67.7 67.9 10% 67.7 73.3 Obs 8 25% 70.6 78.5 Sum of Wgt. 8 50% 79.75 Mean 85.15 Largest Std. Dev. 16.55346 75% 103.1 81 90% 106.6 100.9 Variance 274.0171 95% 106.6 105.3 Skewness .3192319 99% 106.6 106.6 Kurtosis 1.394482 . local x= r(p50) . di `x' 79.75 . local y= round(r(p50),`acc') . di `y' 79.8 Best Regards Richard Fox * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: rounding error***From:*Maarten Buis <maartenlbuis@gmail.com>

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