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possible error in stem() function?

3 messages · Zibeli Aton, Duncan Murdoch, Sarah Goslee

Zibeli Aton
# 
Using R-3.3.1 on Linux I seem to sometimes get inaccurate stem-and-leaf plots using stem.  For example:
+                 510,511,512,514,516,520,524,525,525,527,534,536,542,545,546,547,549,
+                 557,559,561,561,563,563,567,568,569,570,572,578,584)
The decimal point is 1 digit(s) to the right of the |

  46 | 9
  48 | 27344567889
  50 | 3477801246
  52 | 0455746
  54 | 2567979
  56 | 1133789028
  58 | 4

This plot is inaccurate since there are no values 469, 483, 484, etc. in the data.

If I remove one value from the input, then the result appears correct:
+                 510,511,512,514,516,520,524,525,525,527,534,536,542,545,546,547,549,
+                 557,559,561,561,563,563,567,568,569,570,572,578)
The decimal point is 1 digit(s) to the right of the |

  47 | 9
  48 | 27
  49 | 344567889
  50 | 34778
  51 | 01246
  52 | 04557
  53 | 46
  54 | 25679
  55 | 79
  56 | 1133789
  57 | 028

Is there a limit to the length of the input argument, a bug in the function, or something I'm missing?

Thanks.
Duncan Murdoch
#
On 29/08/2016 1:42 PM, Zibeli Aton via R-help wrote:
There's a 479, and a 493, etc.  Since you only have even numbered stems 
you get two decades of leaves on each line.  The ones for the 460's 
would precede the ones for the 470's if there were any; you can see that 
does happen in that the 480's do precede the 490's.

Duncan Murdoch
Sarah Goslee
# 
The help isn't particularly helpful, but you need to play with the
scale argument.
The range of your first dataset is long enough that you're getting
only even-numbered stems by default.


Try these:

x1 <- c(479,482,487,493,494,494,495,496,497,498,498,499,503,504,507,507,508,

510,511,512,514,516,520,524,525,525,527,534,536,542,545,546,547,549,
                 557,559,561,561,563,563,567,568,569,570,572,578,584)
stem(x1, scale=1)
summary(x1)
stem(x1, scale=2)

x2 <- c(479,482,487,493,494,494,495,496,497,498,498,499,503,504,507,507,508,

510,511,512,514,516,520,524,525,525,527,534,536,542,545,546,547,549,
                 557,559,561,561,563,563,567,568,569,570,572,578)
stem(x2, scale=1)
summary(x2)
stem(x2, scale=2)



On Mon, Aug 29, 2016 at 1:42 PM, Zibeli Aton via R-help
<r-help at r-project.org> wrote: