Count number of rows matching a criteria

Question

I am looking for a command in R which is equivalent of this SQL statement  I want this to be a very simple basic solution without using complex functions OR dplyr type of packages   Select count    as number of states    from myTable where  sCode    CA    so essentially I would be counting number of rows matching my where condition   I have imported a csv file into mydata as a data frame So far I have tried these with no avail    nrow mydata sCode     CA          gt  gt  returns NULL sum mydata mydata sCode     CA     na rm T        gt  gt  gives Error in FUN X  1L           only defined on a data frame with all numeric variables sum subset mydata  sCode  CA   select c sCode    na rm T        gt  gt  FUN X  1L           only defined on a data frame with all numeric variables sum mydata sCode     CA   na rm T         gt  gt  returns count of all rows in the entire data set  which is not the correct result    and some variations of the above samples  Any help would be appreciated  Thanks

User · Answer

grep command can be used  CA   mydata grep  quot CA quot   mydata sCode    nrow CA

User · Answer

With dplyr package  Use   nrow filter mydata  sCode     CA       All the solutions provided here gave me same error as multi-sam but that one worked

User · Answer

Call nrow passing as argument the name of the dataset   nrow dataset

User · Answer

mydata sCode is a vector  it s why nrow output is NULL  mydata mydata sCode     CA    returns data frame where sCode     CA   sCode includes character  That s why sum gives you the error  subset mydata  sCode  CA   select c sCode    you should use sCode   CA  instead sCode  CA   Then subset returns you vector where sCode equals CA  so you should use   length subset na omit mydata   sCode  CA   select c sCode       Or you can try this  sum na omit mydata sCode      CA

User · Answer

mydata sCode     CA  will return a boolean array  with a TRUE value everywhere that the condition is met  To illustrate    gt  mydata   data frame sCode   c  CA    CA    AC     gt  mydata sCode     CA   1   TRUE  TRUE FALSE   There are a couple of ways to deal with this    sum mydata sCode     CA    as suggested in the comments  because TRUE is interpreted as 1 and FALSE as 0  this should return the numer of TRUE values in your vector  length which mydata sCode     CA     the which   function returns a vector of the indices where the condition is met  the length of which is the count of  CA     Edit to expand upon what s happening in  2    gt  which mydata sCode     CA    1  1 2   which   returns a vector identify each column where the condition is met  in this case  columns 1 and 2 of the dataframe   The length   of this vector is the number of occurences

User · Answer

to get the number of observations the number of rows from your Dataset would be more valid   nrow dat dat sCode     CA

User · Answer

Just give a try using subset  nrow subset data condition     Example  nrow subset myData sCode     CA

User · Answer

sum is used to add elements  nrow is used to count the number of rows in a rectangular array  typically a matrix or data frame   length is used to count the number of elements in a vector  You need to apply these functions correctly  Let s assume your data is a data frame named  quot dat quot   Correct solutions  nrow dat dat sCode     quot CA quot     length dat sCode dat sCode     quot CA quot    sum dat sCode     quot CA quot

[r] Count number of rows matching a criteria

Examples related to r