R: Sorting data.frame by a column and conditionally deleting of rows -

i've got data.frame in r sample data looks this:

dat <- data.frame(name=c("name1","name1","name1","name1","name2","name2","name2","name2") , survey_year =c(1947,1958,1978,1987,1963,1991,2004,1993), reference_year=c(1934,1947,1974,1947,1944,1987,1993,1987), value=c(10,15,13,20,-2,7,12,-19))  dat        name survey_year reference_year value     1 name1        1947           1934    10     2 name1        1958           1947    15     3 name1        1978           1974    13     4 name1        1987           1947    20     5 name2        1963           1944    -2     6 name2        1991           1987     7     7 name2        2004           1993    12     8 name2        1993           1987   -19 

how sort first reference_year (from lowest highest):

   name survey_year reference_year value 1 name1        1947           1934    10 2 name1        1958           1947    15 3 name1        1987           1947    20 4 name1        1978           1974    13 5 name2        1963           1944    -2 6 name2        1991           1987     7 7 name2        1993           1987   -19 8 name2        2004           1993    12 

and if year in reference_year same, delete 1 covers longer period (from reference_year survey_year) dat , write deleted rows new data.frame?

the data.frame sample data should in end:

  name survey_year reference_year value 1 name1        1947           1934    10 2 name1        1958           1947    15 3 name1        1978           1974    13 4 name2        1963           1944    -2 5 name2        1991           1987     7 6 name2        2004           1993    12 

bondeddust left elegant answer. answer far longer his. but, let me leave it.

dat %>%     arrange(reference_year) %>%     mutate(gap = survey_year - reference_year) %>%     arrange(reference_year, gap) %>%     group_by(name, reference_year) %>%     filter(gap == gap[1]) %>%     arrange(name,reference_year)  #   name survey_year reference_year value gap #1 name1        1947           1934    10  13 #2 name1        1958           1947    15  11 #3 name1        1978           1974    13   4 #4 name2        1963           1944    -2  19 #5 name2        1991           1987     7   4 #6 name2        2004           1993    12  11