IF Statements for Strings in Column Expressions

KNIME Analytics Platform
1

Hi - I want to say
IF left( code , 4 = “DRAM” then “RKW”
ELSEIF left( code ,4 - “DRAQ” then “AQ”
ELSE “UNK” ENDIF

I have tried quite a few of the suggestions here (==, encasing them in $ signs, using curly brackets, etc.) to accomplish this and keep failing. Are strings not an option in Column Expressions? Or am I missing something obvious?

If it can’t be done in Column Expressions is there somewhere it can be done so a node for each individual one is not necessary? Thanks.

2

Hey,

General syntax is Java Script like:

If(condition1) {
  Value1
} else if (condition2) {
value2
} else {
Value3
}

You can have as many else ifs as you like before the last „catch all“ else.

In () the conditions can reference columns, variables or „hardcoded“ numbers / strings etc.

E.g.:

If(left(column(code),4)=="DRAM") {
"RKW"
} else if…
4 Likes
3

Thank you. I think this is saying IF is not an allowable function in Column Expressions. I don’t see it in the function dropdown - where am I going wrong?

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1 Like
4

It looks correct but think you need to put code in quotation marks:

Column(“code“)

Correct if is not in the pre built formula, but Java script works …

Not sure if the code is case-sensitive as well - if the column topic doesn’t fix it try all lower case so if instead of If

If you want a node with pre-built if:

Use the new Expression node (available with 5.3 onwards I think )

2 Likes
5

@mgrau this article has several examples some with if then else. Note that the syntax might differ slightly

6

Thank you! It wanted quotes, not double commas or apostrophes. The devil is in the details. Expression node and the Knime snippets will be a big help too.
if (left(column(“code”),4)==“DRAM”){
“RNW”
}
else if (left(column(“code”),4)==“DRAQ”){
“AQ”
}
else{
“UNK”
}

2 Likes