如何控制 write.table() 输出中的小数位数？

Question

When working with data (eg, in data.frame) the user can control displaying digits by using

options(digits=3) 

and listing the data.frame like this.

ttf.all

When the user needs to paste the data in Excell like this

write.table(ttf.all, 'clipboard', sep='\t',row.names=F)

The digits parameter is ignored and numbers are not rounded.

See nice output

> ttf.all
  year V1.x.x V1.y.x ratio1 V1.x.y V1.y.y ratioR V1.x.x V1.y.x ratioAL V1.x.y V1.y.y ratioRL
1 2006    227    645   35.2     67    645   10.4    150    645    23.3     53    645    8.22
2 2007    639   1645   38.8    292   1645   17.8    384   1645    23.3    137   1645    8.33
3 2008   1531   3150   48.6    982   3150   31.2    755   3150    24.0    235   3150    7.46
4 2009   1625   3467   46.9   1026   3467   29.6    779   3467    22.5    222   3467    6.40

But what is in excel (clipboard) is not rounded. How to control in in write.table() ?

Answer 1

You can use the function format() as in:

write.table(format(ttf.all, digits=2), 'clipboard', sep='\t',row.names=F)

format() is a generic function that has methods for many classes, including data.frames. Unlike round() , it won't throw an error if your dataframe is not all numeric. For more details on the formatting options, see the help file via ?format

Answer 2

Adding a solution for data frame having mixed character and numeric columns. We first use mutate_if to select numeric columns then apply the round() function to them.

# install.packages('dplyr', dependencies = TRUE)
library(dplyr)

df <- read.table(text = "id  year V1.x.x V1.y.x ratio1
a 2006    227.11111    645.11111   35.22222  
b 2007    639.11111   1645.11111   38.22222  
c 2008   1531.11111   3150.11111   48.22222  
d 2009   1625.11111   3467.11111   46.22222",
                 header = TRUE, stringsAsFactors = FALSE)

df %>% 
  mutate_if(is.numeric, round, digits = 2)
#>   id year  V1.x.x  V1.y.x ratio1
#> 1  a 2006  227.11  645.11  35.22
#> 2  b 2007  639.11 1645.11  38.22
#> 3  c 2008 1531.11 3150.11  48.22
#> 4  d 2009 1625.11 3467.11  46.22

### dplyr v1.0.0+
df %>% 
  mutate(across(where(is.numeric), ~ round(., digits = 2)))
#>   id year  V1.x.x  V1.y.x ratio1
#> 1  a 2006  227.11  645.11  35.22
#> 2  b 2007  639.11 1645.11  38.22
#> 3  c 2008 1531.11 3150.11  48.22
#> 4  d 2009 1625.11 3467.11  46.22

^{Created on 2019-03-17 by the reprex package (v0.2.1.9000)}