The scientific algorithm of controlling R language shows two options: digitis and scipen. There is very little information introduced, and some are wrong. After looking through the help of R language and carefully considering the examples, the summary is as follows:
The default settings are:
getOption("digits")
[1] 7
getOption("scipen")
[1] 0
digits The number of valid numeric characters is 7 by default, and the range is [1,22]
scipen The penalty displayed by scientific count can be positive or negative, and the default is 0.
When R outputs numbers, the length represented by ordinary numbers is <= Character length represented by scientific notation + scipen length is retained, otherwise the length represented by scientific notation is used.
Take a chestnut:
> options(digits = 2) # The valid number is 2 digits> options(scipen = 1) > 1 # 1e+00 Length is 5, 1 reserved for display, length is 1[1] 1 > 12345678 # 1.2e+07, length is 7, 7 + scipen = 8, the normal number represents the length is 8, and does not exceed 8, and the representation of different numbers is retained.[1] 12345678 > 123456789 # 1.2e+08, length is 7, 7 + scipen =8, ordinary numbers represent length is 9, so switch to scientific notation representation[1] 1.2e+08
A simple method (not so accurate, for example, when digits=1, there is no decimal point; when the number is very large, the exponent may be 3 digits) can estimate the longest string of numbers like this:
digits + 1 (decimal point) + 4 (e+XX scientific notation) + scipen
For example, the longest number length that is not represented by scientific notation is 2+1+4+1 = 8
Let's see if the modification scipen = -2, verify whether the longest number length is 2+1+4 - 2 = 5
> options(scipen = -2) > 1234 [1] 1234 > 12345 [1] 12345 > 123456 [1] 1.2e+05
really!
Supplement: R language sets the numerical output (retained to the decimal point and retain valid numbers)
In R language, the output of a number is 7 bits by default:
> a = 0.1234567890 #10> a [1] 0.1234568
Note: The output results are rounded.
1 options(digits) function
Set the output length through the options(digits) function, when digits = 3:
> options(digits = 3) > a = 0.1234567890 #10> a [1] 0.123
When digits = 10:
> options(digits = 10) > a = 0.1234567890 #10> a [1] 0.123456789
digits can be 22 at most, and if it exceeds 22, an error will be reported:
> options(digits = 3) > options(digits = 22) > options(digits = 23) Error in options(digits = 23) : invalid 'digits' parameter, allowed 0...22
The output result is only 9 bits, and the end 0 is omitted.
2 round(x, n) function
In the round(x, n) function, x is a number and n is the number of digits reserved after the decimal point. When setting n = 4:
> a = 0.1234567890 #10> round(a, 4) [1] 0.1235 > a = 1.234567890 #9 decimal places> round(a, 4) [1] 1.2346
Note: The output results are rounded.
When setting n = 10:
> a = 0.1234567890 #10> round(a, 10) [1] 0.123456789
The output result is only 9 bits, and the end 0 is omitted.
When the number of 0 after the decimal point exceeds n, the output result is 0:
> a = 0.0001234567890 #13> round(a, 3) [1] 0 > a = 0.0001234567890 #13> round(a, 4) [1] 1e-04
3 signif(y, n) function
In the signif(x, n) function, x is a number and n is the number of significant numbers. When n = 4:
> a = 1.234567890 #9 decimal places> signif(a, 4) [1] 1.235 > a = 0.000001234567890 #15 digits after the decimal point> signif(a, 4) [1] 1.235e-06
When n = 10:
> a = 1.234567890 #9 decimal places> signif(a, 10) [1] 1.23456789
At this time, the 0 at the end of the number is still omitted.
4 sprintf(fmt, …) function
> a = 0.1234567890 #10 digits after the decimal point> sprintf("%0.4f", a)
[1] "0.1235"
> a = 0.1234567890 #10 digits after the decimal point> sprintf("%0.10f", a)
[1] "0.1234567890"
The 0 at the end can be preserved through the sprintf(fmt, ...) function.
When the input is an integer, the number of digits is insufficient and 0 will be added before the input value:
> a = 12456789
> sprintf("%03d", a)
[1] "12456789"
> a = 12
> sprintf("%03d", a)
[1] "012"
Everyone is welcome to criticize and correct me.
The above is personal experience. I hope you can give you a reference and I hope you can support me more. If there are any mistakes or no complete considerations, I would like to give you advice.