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I have two dataframes, the first column of each dataframe is a unique id number (the rest of the columns are data variables). I would like to figure out how many times each id number appears in each dataframe. So far I can use: length( match (dataframeA$unique.id[1], dataframeB$unique.id) ) but this only works on each row of dataframe A one-at-a-time. I would like to do this for all of the rows in dataframe A, and then put the results in a new variable: dataframeA$count I'm new to R, so please be patient with me! Sorry if this question...

Dear kind R helpers, I have a vector of runway names in rwy ("31R", "31L",... the number is user selectable) arrgnd is a data frame with data for all flights and all runways, with a Runway column. I am trying to subset arrgnd into a dat frame for each selected runway, and then combine them back together using the following code: for (j in 1:nr) { # nr = number of

...m> Content-Type: text/plain; charset=us-ascii I have two dataframes, the first column of each dataframe is a unique id number (the rest of the columns are data variables).  I would like to figure out how many times each id number appears in each dataframe.  So far I can use: length( match (dataframeA$unique.id[1], dataframeB$unique.id) ) but this only works on each row of dataframe A one-at-a-time.  I would like to do this for all of the rows in dataframe A, and then put the results in a new variable: dataframeA$count [[elided Yahoo spam]] Sorry if this question has already been answered...