Stat - 1 year ago 60
R Question

# Multiply constant in R

I have vector of numeric with 5 decimal points, I tired to multiply by 7, the result give me integer, I don't know why decimals disappeared. Do you know what happened?

Here is data

``````> df
ID     Begin       End       Int
1   34 30-Dec-05 15-Jan-06  6.142857
2   66  3-Apr-06  7-Aug-06 13.000000
3   66 28-Feb-06  3-Apr-06 17.857143
4  104 31-Jan-06 28-Feb-06  6.000000
5  104 28-Feb-06 23-May-06 10.000000
6  104 24-May-06  7-Sep-06 22.142857
7  182  9-May-06 10-Jul-06 -1.571429
8  189 10-Apr-06 11-Apr-06 15.285714
9  189 12-Apr-06 12-Apr-06 15.571429
10 189 13-Apr-06 15-Apr-06 15.714286
11 189 13-Aug-06 13-Sep-06 23.428571
12 189  6-Jun-06  6-Jun-06 33.142857
13 193 17-Mar-06 24-Mar-06  2.428571
14 193 27-Jun-06 28-Jun-06 17.000000
15 193  7-Jul-06 25-Sep-06 18.428571
16 237 10-Feb-06 15-Mar-06 -2.000000
17 237 15-Mar-06 10-Apr-06  2.714286
18 264 25-Jan-06  7-Nov-06 -2.285714
19 282 19-Nov-05  1-Aug-06  6.000000

df\$cal <- df\$Int*7
``````

It gives me

`````` [1]  43  91 125  42  70 155 -11 107 109 110
[11] 164 232  17 119 129 -14  19 -16  42
``````

R adjusts the print format according to the decimal part of the number; it doesn't necessarily print all the zeros after the decimal point.

``````> (x = 18/7)
[1] 2.571429
> x*7
[1] 18
> sprintf("%1.10f",x*7)
[1] "18.0000000000"
``````

Based on your example, that's exactly what's happening here: your `Int` values are all exact multiples of 1/7 (presumably derived from some sort of conversion from units of days to weeks), so multiplying by 7 gives you floating-point results with exact or nearly-exact decimal parts of `.00000...`

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