Filter data frame rows by a logical condition

Question

I want to filter rows from a data frame based on a logical condition  Let s suppose that I have data frame like     expr value     cell type 1    5 345618 bj fibroblast 2    5 195871 bj fibroblast 3    5 247274 bj fibroblast 4    5 929771          hesc 5    5 873096          hesc 6    5 665857          hesc 7    6 791656          hips 8    7 133673          hips 9    7 574058          hips 10   7 208041          hips 11   7 402100          hips 12   7 167792          hips 13   7 156971          hips 14   7 197543          hips 15   7 035404          hips 16   7 269474          hips 17   6 715059          hips 18   7 434339          hips 19   6 997586          hips 20   7 619770          hips 21   7 490749          hips   What I want to is to get a new data frame which looks the same but only has the data for one cell type  E g  subset   select rows which contains the cell type  hesc       expr value     cell type 1    5 929771          hesc 2    5 873096          hesc 3    5 665857          hesc   Or either cell type  bj fibroblast  or  hesc       expr value     cell type 1    5 345618 bj fibroblast 2    5 195871 bj fibroblast 3    5 247274 bj fibroblast 4    5 929771          hesc 5    5 873096          hesc 6    5 665857          hesc   Is there any easy way to do this   I ve tried   expr expr 2      hesc      1   5 929771   5 873096   5 665857   hesc       hesc       hesc        if the original data frame is called  expr   but it gives the results in wrong format as you can see

User · Answer

we can use data table library    library data table    expr  lt - data table expr    expr cell type     hesc     expr cell type  in  c  hesc   fibroblast      or filter using  like  operator for pattern matching   expr cell type  like   hesc  cell type  like   fibroblast

User · Answer

To select rows according to one  cell type   e g   hesc    use      expr expr cell type     hesc       To select rows according to two or more different  cell type    e g  either  hesc  or  bj fibroblast    use  in    expr expr cell type  in  c  hesc    bj fibroblast

User · Answer

Use subset  for interactive use   subset expr  cell type     hesc   subset expr  cell type  in  c  bj fibroblast    hesc      or better dplyr  filter    filter expr  cell type  in  c  bj fibroblast    hesc

User · Answer

Sometimes the column you want to filter may appear in a different position than column index 2 or have a variable name    In this case  you can simply refer the column name you want to filter as   columnNameToFilter    cell type  expr expr  columnNameToFilter       hesc

User · Answer

I was working on a dataframe and having no luck with the provided answers  it always returned 0 rows  so I found and used grepl   df   df grepl  downlink  df Transmit direction      Which basically trimmed my dataframe to only the rows that contained  downlink  in the Transmit direction column  P S  If anyone can guess as to why I m not seeing the expected behavior  please leave a comment   Specifically to the original question   expr grepl  hesc  expr cell type     expr grepl  bj fibroblast hesc  expr cell type

User · Answer

No one seems to have included the which function  It can also prove useful for filtering    expr which expr cell     hesc       This will also handle NAs and drop them from the resulting dataframe   Running this on a 9840 by 24 dataframe 50000 times  it seems like the which method has a 60  faster run time than the  in  method

User · Answer

This worked like magic for me   celltype hesc bool   expr  cell type       hesc    expr celltype hesc   expr celltype hesc   Check this blog post

User · Answer

You could use the dplyr package   library dplyr  filter expr  cell type     hesc   filter expr  cell type     hesc    cell type     bj fibroblast

User · Answer

The reason expr expr 2      hesc   doesn t work is that for a data frame  x y  selects columns  not rows   If you want to select rows  change to the syntax x y   instead    gt  expr expr 2      hesc      expr value cell type 4   5 929771      hesc 5   5 873096      hesc 6   5 665857      hesc

[r] Filter data.frame rows by a logical condition

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