Syntax and Line Breaks

[TardisPilot]

Hey all, KNIME newbie trying to transition from Alteryx to KNIME.

Is there a document anywhere that breaks down how Expression Syntax works in KNIME? Every time I need to write a formula/expression I find myself struggling.

Also, I am writing a Rule-Based Row Filter using an ‘IN’ expression. There are about 30 strings that need to be present for the IN. Rather than have on massive continuous line is it possible to do a line break to write each string on a separate line? I do this in VBA sometimes and was wondering if it it possible in KNIME.

I really appreciate any guidance on expression/formula writing!

[moritz.heine]

Hi,

the syntax of the Column Expressions and the Variable Expressions are based on a scripting language called JavaScript. Similar to the Math Formula and the String Manipulation nodes, the Column Expressions and Variable Expressions provide functions that can be used. To access the content of a column of the input table you simply call the function column(“COLUMN_NAME”) (or: column(column_index)).

Like in other programming languages, called functions are evaluated starting from the innermost, i.e. if you have an expression like

sqrt(column(“a”))

column(“a”) will be evaluated first and feeding its result (in this case the content of the column called “a”) into the function surrounding it. This way you can combine multiple functions to build a more complex one.
As these expressions get more and more complex and results of calculations may be re-used to feed different functions, you can store values into variables using

=

Example:

col_a = column(“a”)
res = sqrt(col_a)

Now you can re-use col_a and res in the lines to follow. The evaulation of an expression is always from top to bottom.
As the expression engine is based on JavaScript you can also use valid JavaScript syntax (but only up to ECMA 5). This means that you can also use for- and while-loops, if-else-statements and many more.

Cheers,
Moritz

[ipazin]

Hi there!

In addition to what has been said I would add that line break in Rule Engine nodes are not possible as each rule is either line or comment. In order to have each string in its own line you should do 30 rules.

Also considering you are in transition from Alteryx to KNIME I suggest you to check this forum topic:

Considering switching to KNIME from Alteryx

Hi there, In a cost cutting effort I am seriously considering closing my Alteryx account and move the the KNIME platform. I want to be a quick study on this, to see if it right for me and my company. I have read comparisons on line between the two, however, what I am looking for is the string of commands in KNIME that are regularly pulled out of Alteryx… Kind of this is what I do in Alteryx to achieve this, and this is how you do it in KNIME. I know that this is cheating on the learning, I …

And a bit older one:

KNIME vs SAS and Alteryx

Dear users, My company is now in a tool research project analyzing the features of KNIME/SAS/Alteryx for Marketing purposes.  We are now using SPSS Statistics but want to move to a more robust and user friendly tool which makes portability of projects to other employees easier, requires less manual coding and easier to work with.  From the tools we have seen KNIME seems the best fit but because it is open source the IT staff is a bit reluctant to implement as the support might be less than th…

Br,
Ivan

[agaunt]

Hi @TardisPilot, in case your Rule-Based Row Filter is structured like this:

$Column1$ = "Abc" AND $Column2$ = "Bcd" AND .... => TRUE

you could also consider

NOT $Column1$ = "Abc" => FALSE
NOT $Column2$ = "Bcd" => FALSE
...
TRUE => TRUE

Kind regards, agaunt

[TardisPilot]

@moritz.heine, I really appreciate the breakdown!

[TardisPilot]

@ipazin, Thank you! I will check out those posts!