How to find row number of a value in R code

Question

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    gt  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

User · Answer

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

User · Answer

As of R 3 3 0  one may use startsWith   as a faster alternative to grepl     which startsWith mydata 2 height seca1  1578

User · Answer

I would be tempted to use grepl  which should give all the lines with matches and can be generalised for arbitrary strings   mydata 2  lt - read table textConnection   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                           sep        header   TRUE   which grepl 1578  mydata 2 height seca1     The output is    gt  which grepl 1578  mydata 2 height seca1    1  7  gt      Edit  However  as pointed out in the comments  this will capture much more than the string 1578  e g  it also matches for 21578 etc  and thus should be used only if you are certain that you the length of the values you are searching will not be larger than the four characters or digits shown here   And subsetting as per the other answer also works fine   mydata 2 mydata 2 height seca1    1578      sex age height seca1 height chad1 height DL weight alog1 7   F  19         1578         1576       156           50  gt     If you re looking for several different values  you could put them in a vector and then use the  in  operator   look for  lt - c 1578  1658  1616   gt  mydata 2 mydata 2 height seca1  in  look for       sex age height seca1 height chad1 height DL weight alog1 7    F  19         1578         1576       156         50 0 11   F  28         1616         1619       161         65 5 27   M  26         1658         1658       165         69 0  gt

User · Answer

1 nrow mydata 2   mydata 2  4     1578    Of course there may be more than one row with a value of 1578

User · Answer

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    gt  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

[r] How to find row number of a value in R code

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