How to print a row without header and NA values in R -

i have dataframe called decision_tree. need print 1 of row data frame condition. example: student_id == 100.

selected_row <- filter(decision_tree, student_id=100) 

but getting weird error.

error: each variable must 1d atomic vector or list. problem variables: 'student_id'  decision_tree <- plyr::ldply(recommendations, rbind) decision_tree$student_id <- select(r_df, student_id) colnames(decision_tree) <- c("recommended course 1","recommended course 2","recommended course 3","recommended course 4","recommended course 5","student_id") 

data frame looks like:

last field numeric , other fields factors 7 or 9 levels.

even if set colnames null. last column have student_id. , first 5 column names 1 5

structure(list(recommended course 1 = structure(c(na, na, na, 5l, na, na, na, na, 8l, 2l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20dv", "p_f20gp", "p_f20ma", "p_f20mc", "p_f20ro", "p_f20rs"), class = "factor"), recommended course 2 = structure(c(na, na, na, 9l, na, na, na, na, 2l, 7l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20dv", "p_f20gp", "p_f20ma", "p_f20mc", "p_f20ro", "p_f20rs"), class = "factor"), recommended course 3 = structure(c(na, na, na, na, na, na, na, na, 1l, 3l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20gp", "p_f20mc", "p_f20ro"), class = "factor"), recommended course 4 = structure(c(na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_), .label = "p_f20bc", class = "factor"), student_id = structure(list(student_id = c(55l, 68l, 70l, 99l, 100l, 101l, 103l, 105l, 106l, 107l)), .names = "student_id", row.names = c(na, 10l), class = "data.frame")), .names = c("recommended course 1", "recommended course 2", "recommended course 3", "recommended course 4", "student_id"), row.names = c(na, 10l), class = "data.frame")

edit: dput data different image. following code produces results of character(0) because there rows without course recommendations. in comments let me know how handle these.

decision_tree <- structure(list("recommended course 1" = structure(c(na, na, na, 5l, na, na, na, na, 8l, 2l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20dv", "p_f20gp", "p_f20ma", "p_f20mc", "p_f20ro", "p_f20rs"), class = "factor"), "recommended course 2" = structure(c(na, na, na, 9l, na, na, na, na, 2l, 7l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20dv", "p_f20gp", "p_f20ma", "p_f20mc", "p_f20ro", "p_f20rs"), class = "factor"), "recommended course 3" = structure(c(na, na, na, na, na, na, na, na, 1l, 3l), .label = c("p_f20bc", "p_f20dl", "p_f20dp", "p_f20gp", "p_f20mc", "p_f20ro"), class = "factor"),  "recommended course 4" = structure(c(na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_, na_integer_), .label = "p_f20bc", class = "factor"), student_id = structure(list(student_id = c(55l, 68l, 70l, 99l, 100l, 101l, 103l, 105l, 106l, 107l)), .names = "student_id", row.names = c(na, 10l), class = "data.frame")), .names = c("recommended course 1", "recommended course 2", "recommended course 3", "recommended course 4", "student_id"), row.names = c(na, 10l), class = "data.frame")   recommend <- function(studentid){   courses <- grep("course", colnames(decision_tree))   id <- grep("id", colnames(decision_tree))   rows <- which(decision_tree[,id] == studentid)   x <- decision_tree[rows,courses][!is.na(decision_tree[rows,courses])]   if(length(x) == 0) {     paste("no course recommend")   } else {     x   } } recommend(99)      "p_f20gp" "p_f20rs"  for(i in 1:nrow(decision_tree)){   print(recommend(decision_tree$student_id[i,])) } [1] "no course recommend" [1] "no course recommend" [1] "no course recommend" [1] "p_f20gp" "p_f20rs" [1] "no course recommend" [1] "no course recommend" [1] "no course recommend" [1] "no course recommend" [1] "p_f20ro" "p_f20dl" "p_f20bc" [1] "p_f20dl" "p_f20mc" "p_f20dp"