Statistics/Basic: Difference between revisions
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J: closer reading of task requirements |
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=={{header|J}}== |
=={{header|J}}== |
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J has library routines to compute standard deviation: |
J has library routines to compute mean and standard deviation: |
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<lang j> require'statfns' |
<lang j> require'statfns' |
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stddev ?1000#0 |
(mean,stddev) ?1000#0 |
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0.484669 0.287482 |
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0.294753 |
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stddev ?10000#0 |
(mean,stddev) ?10000#0 |
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0.503642 0.290777 |
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0.289972 |
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stddev ?100000#0 |
(mean,stddev) ?100000#0 |
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0. |
0.499677 0.288726</lang> |
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but they are not quite what is being asked for here. |
but they are not quite what is being asked for here. |
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Instead: |
Instead: |
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<lang j> |
<lang j>meanstddevP=:3 :0 |
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NB. compute std dev of y random numbers |
NB. compute mean and std dev of y random numbers |
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NB. picked from even distribution between 0 and 1 |
NB. picked from even distribution between 0 and 1 |
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t=. 0 |
s=.t=. 0 |
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for_n.i.<.y%1e6 do. |
for_n.i.<.y%1e6 do. |
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s=.s+ +/ data=. ?1e6#0 |
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t=.t+ +/(data-0.5)^2 |
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end. |
end. |
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s=.s+ +/ data=. ?(1e6|y)#0 |
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t=.t++/(data-0.5)^2 |
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%:t%y |
(s%y),%:t%y |
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)</lang> |
)</lang> |
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For a histogram: |
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<lang j>histogram=: <: @ (#/.~) @ (i.@#@[ , I.) |
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require'plot' |
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plot ((%*1+i.)100) ([;histogram) ?10000#0</lang> |
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(should upload an image generated this way) |
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Example use: |
Example use: |
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<lang j> |
<lang j> meanstddevP 1000 |
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0.501617 0.288271 |
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0.281084 |
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meanstddevP 10000 |
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0.49732 0.290061 |
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0.287244 |
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meanstddevP 100000 |
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0. |
0.498912 0.289179</lang> |
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(That said, note that these numbers are random, so reported standard deviation will vary with the random sample being tested.) |
(That said, note that these numbers are random, so reported standard deviation will vary with the random sample being tested.) |
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