conditional awk statement to create a new field with additive value - dataframe

Question

Question
How would I use awk to create a new field that has $2+consistent value?
I am planning to cycle through a list of values but I wouldn't mind using a one liner for each command
PseudoCode
awk '$1 == Bob {$4 = $2 + 400}' file
Sample Data
Philip 13 2
Bob 152 8
Bob 4561 2
Bob 234 36
Bob 98 12
Rey 147 152
Rey 15 1547
Expected Output
Philip 13 2
Bob 152 8 408
Bob 4561 2 402
Bob 234 36 436
Bob 98 12 412
Rey 147 152
Rey 15 1547

Answer 1

just quote Bob, also you want to add third field not second
$ awk '$1=="Bob" {$4=$3+400}1' file | column -t
Philip 13 2
Bob 152 8 408
Bob 4561 2 402
Bob 234 36 436
Bob 98 12 412
Rey 147 152
Rey 15 1547

Answer 2

Here , check if $1 is equal to Bob and , reconstruct the record ($0) by appending $2 FS 400 in to $0. Here FS is the field separator used between 3rd and 4th fields. 1 in the end means tell awk to take the default action which is print.
awk '$1=="Bob"{$0=$0 FS $2 + 400}1' file
Philip 13 2
Bob 152 8 552
Bob 4561 2 4961
Bob 234 36 634
Bob 98 12 498
Rey 147 152
Rey 15 1547
Or , if you want to keep name(Bob) as variable
awk -vname="Bob" '$1==name{$0=$0 FS $2 + 400}1' file

Answer 3

1st solutiuon: Could you please try following too once. I am using here NF and NF+1 awk's out of the box variables. Where $NF denotes value of last column of current line and $(NF+1) will create an additional column if condition of st field stringBob` is found is TRUE.
awk '{$(NF+1)=$1=="Bob"?400+$NF:""} 1' OFS="\t" Input_file
2nd solution: In case we don't want to create a new field and simply want to print the values as per condition then try following, this should be more faster I believe.
awk 'BEGIN{OFS="\t"}{$1=$1;print $0,$1=="Bob"?400+$NF:""}' Input_file
Output will be as follows.
Philip 13 2
Bob 152 8 408
Bob 4561 2 402
Bob 234 36 436
Bob 98 12 412
Rey 147 152
Rey 15 1547
Explanation: Adding explanation for above code now.
awk ' ##Starting awk program here.
{
$(NF+1)=$1=="Bob"?400+$NF:"" ##Creating a new last field here whose value will be depending upon condition check.
##its checking condition if 1st field is having Bob string in it then add 400 value to last field value or make it NULL.
}
1 ##awk works on method of condition then action. so by mentioning 1 making condition TRUE here and NO action defined so by default print of current line will happen.
' OFS="\t" Input_file ##Setting OFS as TAB here where OFS ois output field separator and mentioning Input_file name here.