## Friday, 6 February 2015

### Number formatting

For presentation of numeric tables in reports, one often has to use '000 separators and use equal spacing to make the results look neater and pretty.

formatC() in the base package is useful for this purpose.

Example 1:

Given the below input
data.frame(V1=c((-1:1)/0,c(1,100)*pi))
V1
1       -Inf
2        NaN
3        Inf
4   3.141593
5 314.159265

converted to below
data.frame(V1=formatC(c((-1:1)/0,c(1,100)*pi), width = 8, digits = 1))
V1
1     -Inf
2      NaN
3      Inf
4        3
5    3e+02

Alternatively for 2 digits displayed
data.frame(V1=formatC(c((-1:1)/0,c(1,100)*pi), width = 8, digits = 2))
V1
1     -Inf
2      NaN
3      Inf
4      3.1
5  3.1e+02

Example 2:

Given the below numbers

12344448.2
3244149.9210001
321.21
78186271.32155

To only show integers
data.frame(V1=formatC(c(12344448.2,3244149.9210001,3217747.214,78186271.32155),format="d"))
V1
1 12344448
2  3244149
3  321
4 78186271

To show numbers with scientific format

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="e"))
V1
1 1.2344e+07
2 3.2441e+06
3 3.2121e+02
4 7.8186e+07

To show numbers with scientific format when the number is big

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="g"))
V1
1 1.234e+07
2 3.244e+06
3     321.2
4 7.819e+07

To show numbers in its actual form (this is limited by the options setting in R)

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="f"))
V1
1 12344448.2000
2  3244149.9210
3      321.2100
4 78186271.3215

To show remainder of digits in decimal points, specify 'digits' parameter (but format="f" will change the original input to comply with the new setting - so this should be used when you want to round off figures to smaller number of digits)

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="f",digits=15))
V1
1 12344448.199999999254942
2  3244149.921000100206584
3      321.209999999999980
4 78186271.321549996733665

Use format="fg" in combination with 'digits' specification to display the actual input

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="fg",digits=15))
V1
1       12344448.2
2  3244149.9210001
3           321.21
4   78186271.32155

To insert '000 separator

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="fg",digits=15,big.mark=","))
V1
1      12,344,448.2
2 3,244,149.9210001
3            321.21
4  78,186,271.32155

To make the decimal point more obvious

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="fg",digits=15,big.mark=",",decimal.mark="\\"))
V1
1      12,344,448\\2
2 3,244,149\\9210001
3            321\\21
4  78,186,271\\32155

To insert separators in the decimal points

data.frame(V1=formatC(c(12344448.2,3244149.9210001,321.21,78186271.32155),format="fg",digits=15,big.mark=",",decimal.mark="\\",small.mark=" "))
V1
1       12,344,448\\2
2 3,244,149\\92100 01
3             321\\21
4   78,186,271\\32155