Hi ,everyone , I draw some boxplot figure with the command "boxplot".But in the figure,there are some bubbles at the top part of the figure. Can anyone tell me what the correct meaning of these bubbles?and how to remove it? -- TANG Jie Email: totangjie@gmail.com Tel: 0086-2154896104 Shanghai Typhoon Institute,China [[alternative HTML version deleted]]
Jie TANG wrote:> Hi ,everyone , > I draw some boxplot figure with the command "boxplot".But in the > figure,there are some bubbles at the top part of the figure. > > Can anyone tell me what the correct meaning of these bubbles?and how to > remove it?See some textbook about boxplots. For very short: These "bubbles" are probably some values of your data outside 1.5 x interquartilerange from the .25/.75 quartiles. Uwe Ligges
On Mon, 2009-07-20 at 11:18 +0800, Jie TANG wrote:> Hi ,everyone , > I draw some boxplot figure with the command "boxplot".But in the > figure,there are some bubbles at the top part of the figure. > > Can anyone tell me what the correct meaning of these bubbles?and how to > remove it?Do you mean the points (circles) shown for example in:> set.seed(123) > dat <- rt(10000, df = 3) > boxplot(dat)?? If so, these are your *data* and shouldn't be removed. These are the points that lie further than 1.5 * the length of the box, with a caveat explained on ?boxplot.stats You could do> boxplot(dat, range = 0)But the resulting plot will require explanation to those used to see a boxplot sensu Tukey. G -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
On Mon, Jul 20, 2009 at 5:18 AM, Jie TANG<totangjie at gmail.com> wrote:> Hi ,everyone , > ?I draw some boxplot figure with the command "boxplot".But in the > figure,there are some bubbles at the top part of the figure. > > ?Can anyone tell me what the correct meaning of these bubbles?and how to > remove it?Those are data points that are considered to be outliers. As to how to remove them, that's a tricky question, more as to why than how. The purpose of showing those points in a different way is to emphasize that those points deserve special attention. You do not want to just "make them go away".
On Mon, Jul 20, 2009 at 5:18 AM, Jie TANG<totangjie at gmail.com> wrote:> ?Can anyone tell me what the correct meaning of these bubbles?and how to > remove it?Have a look at the Wikipedia entry on box plots: http://en.wikipedia.org/wiki/Boxplot Why do you want to remove the bubbles? They are outliers and part of your data. -- Michael Knudsen micknudsen at gmail.com http://lifeofknudsen.blogspot.com/
Jie TANG wrote:> Hi ,everyone , > I draw some boxplot figure with the command "boxplot".But in the > figure,there are some bubbles at the top part of the figure. > > Can anyone tell me what the correct meaning of these bubbles?and how to > remove it? >Hi Jie, At a wild guess, the "bubbles" may be outliers. Have you checked for any values in your data that are much larger than all the rest? Jim