Truncating string signals

[PabloR]

I would like to truncate string signals to a given number of characters.

As an example, say the signal gives a combination of an #ID_date_Initials (e.g. 12345_20200326_PJR).

How can I generate a new signal that contains only part of the string? 

In the example above, I would like to get only the #ID.

[Thorsten Vogt]

Hi Pablo,

you can use transform() and replace() to do this. I made an example with a signal that contains the following data:

To create a signal that contains only the numeric values I used the following formula:

$originalSignal.transform(($p, $c) -> sample($c.getKey(), $c.getValue().replace('/\\w+\\s(\\d+)/', '$1')))

Transform is used to access every sample in the signal by specifying a lambda expression. The current sample is temporarily stored in the variable $c. $p contains the previous sample which is not used here. For each sample of the original signal a new sample is created by using the timestamp (key) of the original sample. The value for the new sample is determined by the value of the sample of the original signal on which replace() is executed. As the name suggests replace() is used to replace portions of a string. In this case I make use of a regular expression to determine the numeric value inside the original string and replace the original string by the determined value. The result looks like this:

For your example (12345_20200326_PJR) you have to modify the replace part to:

.replace('/(\\d+)_\\d+_\\w+/', '$1')

Hope this helps.

Regards,

Thorsten

 

[Teddy]

The replace operator can be applied a signal without a transform.  Using the replace function without the transform will be less computationally expensive, resulting in better performance. Both ways will get to the same answer.

Syntax for replace function without transform:

$signal.replace('/(\\d+)_\\d+_\\w+/', '$1')

 

[Morgan Bowling]

Elaborating on this, 

If you just want to grab the first character of your string you can do 

$siganl.replace('/(.).*/','$1')

and the second character would be 

$siganl.replace('/.(.).*/','$1')

and so on.

Morgan