Table Row to Variable Loop Start

KCH Workflows
1

This workflow demonstrates the usage of the 'Table Row to Variable Loop Start' node.

This is a companion discussion topic for the original entry at https://kni.me/w/g_W4wvGJ-PrikNkj
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quote=“DavisRogers, post:10, topic:14572”
I am down to another challenge that is popping out at me with Parameters.
I have a Form that produces a Orders Table.

I want to have the Orders Table provide the parameters using the Table Row to Variables Loop Start and Loop End.

The form will collect variables that will perform calculations to produce a Dataset. Each Row in the Table is to be a Parameter of 7 or more variables.
How does one set that up? I am looking at a example below that appears to have 1 parameter, but I need about 15.

knime://LOCAL/Example%20Workflows/workflow_SQL-group/12_Using_TableRows_as_FlowVariables_in_Loop

Davis

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Hi,

The Table Row to Variables Loop Start node iterates over the rows in the input table one at at time. For each iteration, the Table Row to Variables Loop Start node generates as many flow variables as there are columns in the input table, and the names of these flow variables are the same as the column names. The values of the flow variables are the values in the row that is handled in the current iteration. In the loop body, you can perform calculations/transformations on these flow variable values. Please have a look at the workflow attached that demonstrates this.

I hope this answers your question. If not, keep asking!

Best,
Maarit

Using_TableRows_as_FlowVariables_in_Loop_demo.knwf (15.7 KB)

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Awesome Maarit,

I am finding the node to be appropriate for this challenge, however, the following error is occorruing

WARN File Reader 2:292 Can’t access ‘file:/C:/Users/Johnny/knime-workspace/OTHER/KNIME_-SB_6-10–2019_0433PM/data/pro_New-Construction-Crawl-Brick.txt’. (C:\Users\Johnny\knime-workspace\OTHER\KNIME_-SB_6-10–2019_0433PM\data\pro_New-Construction-Crawl-Brick.txt (The system cannot find the path specified))

The node this is happening on is the “Rule Based row-filter” node.
The location on my local hard-rive is not file:/C:/Users/Johnny but file:/C:/Users/Davis.

How does this get changed to the proper path from on node? Please advise.

Davis

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Hi Davis,

Could you send a screenshot of the workflow or the workflow file so that I can better understand which nodes you use and which node fails?

Is this user “Johnny” someone who built the workflow and shared it with you? If yes, then I recommend to access the file via a path that is independent of the file structure on the local system, i.e. a workflow-relative path.

Please let me know - I’m happy to help more!

Maarit

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Hi Maarit,

Is this something we can do off public view? This is proprietary information that I would like to remain intellectual property? Please advise.

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HI Davis,

Can you send me just a screenshot of your workflow? If I cannot solve the problem by looking at it, let’s try to find another solution then.

Maarit

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Here is a screenshot of the workflow.

Flow_Variable_Issue_1
Flow_Variable_Issue_1852×189 10.2 KB
Flow_Variable_Issue_2
Flow_Variable_Issue_21009×656 29.5 KB
Google_Spreadsheet_Output_1
Google_Spreadsheet_Output_1798×547 23.8 KB
List_Files_1
List_Files_1760×171 8.95 KB
List_Files_2

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Hi Davis,

I see that

  1. You list files in the “KNIME_DB_WEB…” folder. As an output you get two columns: “Location” and “URL”.
  2. You filter the data that contains the file locations and URLs to rows that have the value of the flow variable “6/11/2019…” in their location values.
  3. You read a file and provide the file path as a flow variable.

A few comments/questions:

  • What is actually the condition that you want to use to filter files when you use the Rule-based Row Filter node? Since you filter by a flow variable value, I cannot see it from the screenshots.
  • Are you trying to read multiple files? If yes, remember to use the Table Row to Variable Loop Start node in that case.
  • Why do you use the Table Row to Variable node in your workflow? The Table Row to variable node converts the first values in Location and URL columns to flow variables that you can use to define the file path in the File Reader node. However, without a loop structure, other files than that given by the first row will never be read.

I attach a simple example of how to read multiple files using a loop. Maybe it helps you more.

Read_many_files.knwf (285.7 KB)

Best,
Maarit

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OK, I am looking at the Read_many_files.knwf and see how this works. Thanks

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Good day all! I need your help on this. I plan to create a loop that will iterate from column to column and then divide the values on that column to the value which matches values on second table with corresponding row. workflow table1 table2
Pls. help! Thanks in advance.

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For ex. Row1 value under M-105(1st table) divided by value on column5(2nd table) on M-105row

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For folks who stumble across this topic in the future, @ikesh 's question was answered in this thread:

:slight_smile: