function to get the power of a number

Question

looking for a way to get from an floating point number the power of 10 to which it is noted

6.45e-8 - would be 8

3.21e-4 would be 4

0.013 would be 2

or minus in all

is ther e a function which would do the following instead of multiplying with 6.45e_8 it would be at first dividing by 1e-8 and then multiply with (6.45e-8/1e8=...).

rolled back to restore original (answered) question. Questions shouldn't undergo "fundamental" edits after they have been answered. — Gregor Thomas, Jun 18 '15 at 18:31
Here's yet another version of the question... http://stackoverflow.com/questions/30923341/multiplication-r-without-float — RHertel, Jun 18 '15 at 18:55

score 5 · Answer 1 · answered Jun 18 '15 at 18:26

5

How about

floor(log10(x))

? log10 computes the log base 10, floor finds the next smaller integer.

answered Jun 18 '15 at 18:26

Ben Bolker

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yes, your solution is more complete (mine does solve the OP's original stated question/set of test cases) – Ben Bolker Jun 18 '15 at 20:51

RHertel · Answer 2 · 2015-06-18T18:45:36.443

1

tenexp <- function(x){c <- trunc(log10(abs(x))); return(abs(c-1*(c<0)))}

Here's the (desired?) result:

> tenexp(0.0134)
[1] 2
> tenexp(6.45e-8)
[1] 8
> tenexp(6.45e+3)
[1] 3
> tenexp(-1.28e+4)
[1] 4

edited Jun 18 '15 at 18:45

answered Jun 18 '15 at 18:39

RHertel

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function to get the power of a number

2 Answers2