[R] hist clarification

[Duncan Murdoch]

On 5/20/2008 2:51 PM, John Gant wrote:
> Can someone help me with a misunderstanding I'm having with hist? I
> expected, from the example below, that the number of bins would always be 10
> and the length of the counts array the same. According to the help section
> 'breaks' can be a integer indicating the number of bins. From the example
> below, the number of bins (length of the counts array) varies. Am I wrong in
> expecting the same number of bins every time from my hist() call (am I doing
> something wrong)?

Your expectation is wrong.  When breaks is a single integer, it's a 
suggestion, it's not fixed.  This is described on the help page:

  "In the last three cases the number is a suggestion only."

If you want to fix the locations of the breaks specify them explicitly.

Duncan Murdoch

> 
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   2  10  18  41  85 151 188 195 149  92  48  14   5   2
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   1   5  19  39  89 155 207 179 162  89  32  19   3   1
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   2   3  19  46 101 149 196 204 137  79  43  16   4   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   2   6  19  41  89 166 188 193 151  87  37  14   6   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   2   6  26  48  90 145 188 177 143  95  52  19   9
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   8  14  35 101 148 195 197 158  82  34  20   8
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   2  12  17  57  82 157 196 215 135  80  25  19   3
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   1   3  14  51  86 130 212 194 152  89  45  18   5
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   1   4  18  46 112 146 173 195 155  93  38  11   7   0   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   1   2  13  39  97 148 198 189 145 101  40  26   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   4  11  39 102 128 191 204 148 111  49  11   1   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
> [1]   1   0  19 136 354 309 160  20   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   3   3  19  52  95 148 198 179 136 100  41  18   7   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
>  [1]   2   4  18  39  88 155 178 188 170  88  46  18   5   1
>> hist(rnorm(1000),breaks=10,plot=FALSE)$counts;
> [1]   1   1  17 125 372 335 126  23
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   3  21  36  88 153 194 196 158  96  38  13   3   1
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   6  18  37  77 155 213 201 130 105  42  11   4   1
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   2   2  21  35  80 155 181 199 165  99  37  16   8
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   1   4  19  49  93 143 201 216 136  79  38  13   7   1
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   1   3  19  38 100 138 208 182 147  93  48  18   5
>> hist(rnorm(1000),breaks=10)$counts;
> [1]   1   0  22 122 331 342 156  25   1
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   2   8  10  48  98 154 170 194 168  91  40  15   2
>> hist(rnorm(1000),breaks=10)$counts;
> [1]   3  17 127 350 355 120  25   3
>> hist(rnorm(1000),breaks=10)$counts;
>  [1]   3   6   8  43  81 151 188 216 163  85  33  15   7   1
> 
> Thanks,
> John
> 
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> 
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