Change a tuple using pig - tuples

Question

I need to substitute characters of a tuple using Pig UDF. For eg, if i have a line in the file as "hello world, Hello WORLD, hello\WORLD" required to be transformed as "hello_world,hello_world,hello_world". To accomplish this, i tried below UDF:
package myUDF;
import java.io.IOException;
import org.apache.pig.EvalFunc;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
public class ReplaceValues extends EvalFunc<Tuple>
{
public Tuple exec(Tuple input) throws IOException {
if (input == null || input.size() == 0)
return null;
try{
String str = (String)input.get(0);
str=str.replace(" ", "_");
str=str.replace("/","");
str=str.replace("\\","");
TupleFactory tf = TupleFactory.getInstance();
Tuple t = tf.newTuple();
t.append(str);
return t;
}catch(Exception e){
throw new IOException("Caught exception processing input row ", e);
}
}
}
but when calling this UDF via pig script i am facing issues, please help me in resolving this:
A = load '/user/cloudera/Stage/ActualDataSet.csv' using PigStorage(',') AS (Rank:chararray,NCTNumber:chararray,Title:chararray,Recruitment:chararray);
B = FILTER A by Rank == 'Rank';
C = FOREACH B GENERATE PigUDF.ReplaceValues(B);
Error: Pig script failed to parse:
Invalid scalar projection: B : A column needs to be projected from a relation for it to be used as a scalar

Answer 1

You have to pass the field that you are trying to modify and not the relation B.Assuming the field that you are trying to match is Title, then you would call the UDF like below
C = FOREACH B GENERATE B.Rank,B.NCTNumber,PigUDF.ReplaceValues(B.Title),B.Recruitment;
Note that if you are trying to replace it in the entire record then your load statement is incorrect.You will have to load the entire record as one line:chararray and then pass the line to your UDF.
Also, instead of an UDF you can use REGEX to match and replace the string of your choice.

Answer 2

In your Pig script, you are passing entire Bag "B" in the UDF, while it accepts tuple as an argument.
Instead pass the field like B.Title as given below.
C = FOREACH B GENERATE PigUDF.ReplaceValues(B.Title);
you can call this UDF on other fields also in the same line as:
C = FOREACH B GENERATE PigUDF.ReplaceValues(B.Title), PigUDF.ReplaceValues(B.Rank);