In the following set of values how can I find the row number of a particular value in column 4 ??
For example how can I find the row number of the value "1578" that's in column number 4 using the R code commands.
> mydata_2
sex age height_seca1 height_chad1 height_DL weight_alog1
1 F 19 1800 1797 180 70.0
2 F 19 1682 1670 167 69.0
3 F 21 1765 1765 178 80.0
4 F 21 1829 1833 181 74.0
5 F 21 1706 1705 170 103.0
6 F 18 1607 1606 160 76.0
7 F 19 1578 1576 156 50.0
8 F 19 1577 1575 156 61.0
9 F 21 1666 1665 166 52.0
10 F 17 1710 1716 172 65.0
11 F 28 1616 1619 161 65.5
12 F 22 1648 1644 165 57.5
13 F 19 1569 1570 155 55.0
14 F 19 1779 1777 177 55.0
15 M 18 1773 1772 179 70.0
16 M 18 1816 1809 181 81.0
17 M 19 1766 1765 178 77.0
18 M 19 1745 1741 174 76.0
19 M 18 1716 1714 170 71.0
20 M 21 1785 1783 179 64.0
21 M 19 1850 1854 185 71.0
22 M 31 1875 1880 188 95.0
23 M 26 1877 1877 186 105.5
24 M 19 1836 1837 185 100.0
25 M 18 1825 1823 182 85.0
26 M 19 1755 1754 174 79.0
27 M 26 1658 1658 165 69.0
28 M 20 1816 1818 183 84.0
29 M 18 1755 1755 175 67.0
This question is related to
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(1:nrow(mydata_2))[mydata_2[,4] == 1578]
Of course there may be more than one row with a value of 1578.
As of R 3.3.0, one may use startsWith() as a faster alternative to grepl():
which(startsWith(mydata_2$height_seca1, 1578))
If you want to know the row and column of a value in a matrix or data.frame, consider using the arr.ind=TRUE argument to which:
> which(mydata_2 == 1578, arr.ind=TRUE)
row col
7 7 3
So 1578 is in column 3 (which you already know) and row 7.
Instead of 1:nrow(mydata_2) you can simply use the which() function: which(mydata_2[,4] == 1578)
Although as it was pointed out above, the 3rd column contains 1578, not the fourth:
which(mydata_2[,3] == 1578)
Source: Stackoverflow.com