This node provides the possibility to append an
arbitrary number of
columns or modify existing columns using expressions.
For each column
that shall be appended or modified a separate expression
is defined.
These expressions can be simply created using predefined functions
similar to
the
Math Formula
and
String Manipulation
Nodes. Nevertheless there is no restriction on the number of lines
an
expression has and the number of functions it uses. This allows
the
user to create their own complex expressions.
Additionally, intermediate results of functions or calculations can
be stored
within an expression by assigning them to variables
(using
'=').
This allows
results to be reused in different parts
of the
expression
after they
have been assigned (see Examples).
Note:
the names of these variables must be different from all of the
names
of
the predefined
functions. Otherwise an error will occur.
To add/remove an expression, the "+"/ "-" buttons respectively have
to
be used.
To edit an expression for an output column, the expression
has
to be
selected in the list of expressions and can be modified in
the
Expression Editor.
The created expressions are
executed row-wise on the
input data.
Available flow variables and
columns of the input table can
be
accessed
via
the provided access functions variable("variableName") and
column("columnName").
Newly
created
columns are
appended
in the
order they
were
defined (top to
bottom) whereas replaced
columns will
remain at
the
original position of
the input table. For
each expression
the last
computed instruction will
be returned.
The syntax and grammar of the expressions are based on the
JavaScript
Languange
.
Examples:
-
5*7+3
will append a column with the value 38 for each row.
-
salary = column("salary")
salary + salary*0.1
will append a column with the values of the salary column of the input table increased by 10%.
-
"a1"
"a2"
will append a column with the value "a2" for each row, whereas
a1 = "a1"
a2 = "a2"
a1
will append a column with the value "a1" for each row.
-
and(column("age") < 26, not(column("student"))
will append a column with true values for everyone under the age of 26 who is not a student, and false for every other person. In this case and(...) and not(...) are predefined functions provided by the Expression Editor.
Options
General
Expression Table
Expression Editor
Advanced
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Links
- Adding Columnsby izaychik63 on 2018-11-27forum.knime.com/p/50441
- Date and Time Manipulationby armingrudd on 2019-09-24forum.knime.com/p/70840
- Find and Replaceby izaychik63 on 2019-03-29forum.knime.com/p/57715
- String Flow Variable and Rule Engineby armingrudd on 2019-04-22forum.knime.com/p/59138
- Adding a zero depending on lenght of stringby johannes.schweig on 2018-10-25forum.knime.com/p/49101
- Show all 95 links
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