Adding a one dataframe to the end of another data.frame in R

I'm having difficulty adding one to the bottom of another data frame. I have one data frame (let's call it DF1) that has 1 row and 5 columns. I have another dataframe (lets call it DF2) that has 50 rows, and 5 columns. I set it up such that the columns between BOTH data frames match - they have the same columns. In fact, DF1 is a calculation based on DF2. This is what DF1 looks like: ``` row.names pt1 pt2 pt3 pt4 calc 0.93 0.45 0.28 0.54 ``` This is what DF2 looks like: ``` row.names pt1 pt2 pt3 pt4 SNP1 AA AG AG AA SNP2 CT CT TC CC SNP3 GG CG CG <NA> SNP4 AA GG AG AA SNP5 <NA> <NA> <NA> <NA> ``` DF1 is supposed to be the the number of actual data points(# of values that is not missing) divided by the total number of possible values. SO.. I want to add DF1 to the bottom of DF2 to look like this: ``` row.names pt1 pt2 pt3 pt4 SNP1 AA AG AG AA SNP2 CT CT TC CC SNP3 GG CG CG <NA> SNP4 AA GG AG AA SNP5 <NA> <NA> <NA> <NA> calc 0.93 0.45 0.28 0.54 ``` When I tried using ``` both.dfs <- rbind(DF1, DF2) # DF1 is first here ``` DF1 is the first row in DF2. I NEED it to be the LAST row. When I tried using ``` both.dfs <- rbind(DF2, DF1) # DF2 is first here ``` I get an error: ``` Warning messages: 1: In `[<-.factor`(`*tmp*`, iseq, value = 0.84) : invalid factor level, NAs generated 2: In `[<-.factor`(`*tmp*`, iseq, value = 0.84) : invalid factor level, NAs generated 3: In `[<-.factor`(`*tmp*`, iseq, value = 0.84) : invalid factor level, NAs generated 4: In `[<-.factor`(`*tmp*`, iseq, value = 0.74) : invalid factor level, NAs generated ``` I've tried merge, I've tried adding a new row to DF2 and then subbing in the values of DF2..nothing seems to work! I'm in desperate need of some help! Anyone?