Deleting all keys that have null values

up vote
8
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I have a notebook that I am working on that starts with an imported CSV file. Many of the rows have blank data in them. I have used the following command to establish a list of associations:

test = AssociationThread[First[rawdata] -> #] & /@ Rest[rawdata]

The InputForm of the above code produces an end result that is something like this:

test = >, <

I want to remove the associations that have blank values so my end result would be more like this:

test2 = "A" -> 1, "B" -> 2

Is there a simple way to drop all keys across all the entries that have null values? I have looked into KeyDrop / KeyDropFrom but can't figure out a way to drop a key based on its value.

Based on this thread, I am thinking there may be a way to use Position or PositionIndex.

Thoughts?

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

add a commentÂ |Â

up vote
8
down vote

favorite

I have a notebook that I am working on that starts with an imported CSV file. Many of the rows have blank data in them. I have used the following command to establish a list of associations:

test = AssociationThread[First[rawdata] -> #] & /@ Rest[rawdata]

The InputForm of the above code produces an end result that is something like this:

test = >, <

I want to remove the associations that have blank values so my end result would be more like this:

test2 = "A" -> 1, "B" -> 2

Is there a simple way to drop all keys across all the entries that have null values? I have looked into KeyDrop / KeyDropFrom but can't figure out a way to drop a key based on its value.

Based on this thread, I am thinking there may be a way to use Position or PositionIndex.

Thoughts?

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

add a commentÂ |Â

up vote
8
down vote

favorite

I have a notebook that I am working on that starts with an imported CSV file. Many of the rows have blank data in them. I have used the following command to establish a list of associations:

test = AssociationThread[First[rawdata] -> #] & /@ Rest[rawdata]

The InputForm of the above code produces an end result that is something like this:

test = >, <

I want to remove the associations that have blank values so my end result would be more like this:

test2 = "A" -> 1, "B" -> 2

Is there a simple way to drop all keys across all the entries that have null values? I have looked into KeyDrop / KeyDropFrom but can't figure out a way to drop a key based on its value.

Based on this thread, I am thinking there may be a way to use Position or PositionIndex.

Thoughts?

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

I have a notebook that I am working on that starts with an imported CSV file. Many of the rows have blank data in them. I have used the following command to establish a list of associations:

test = AssociationThread[First[rawdata] -> #] & /@ Rest[rawdata]

The InputForm of the above code produces an end result that is something like this:

test = >, <

I want to remove the associations that have blank values so my end result would be more like this:

test2 = "A" -> 1, "B" -> 2

Is there a simple way to drop all keys across all the entries that have null values? I have looked into KeyDrop / KeyDropFrom but can't figure out a way to drop a key based on its value.

Based on this thread, I am thinking there may be a way to use Position or PositionIndex.

Thoughts?

associations

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

edited 2 days ago

asked Sep 9 at 16:51

kickert

53015

asked Sep 9 at 16:51

kickert

53015

asked Sep 9 at 16:51

kickert

53015

add a commentÂ |Â

2 Answers
2

active

oldest

votes

up vote
6
down vote

accepted

Try this:

DeleteCases[test, "", 2]

>, <

Since this is about a list of associations, the level on which to search the pattern "" is level 2 (only), therefore the 2 as third argument.

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

add a commentÂ |Â

up vote
6
down vote

Select:

Select[# != "" &] /@ test

"A" -> 1, "B" -> 2

DeleteMissing:

DeleteMissing[test /. "" -> Missing, 2]

<

AssociationMap:

AssociationMap[If[#[[2]] == "", Nothing, #] &] /@ test

>

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

2

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

add a commentÂ |Â

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
6
down vote

accepted

Try this:

DeleteCases[test, "", 2]

>, <

Since this is about a list of associations, the level on which to search the pattern "" is level 2 (only), therefore the 2 as third argument.

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

add a commentÂ |Â

up vote
6
down vote

accepted

Try this:

DeleteCases[test, "", 2]

>, <

Since this is about a list of associations, the level on which to search the pattern "" is level 2 (only), therefore the 2 as third argument.

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

add a commentÂ |Â

up vote
6
down vote

accepted

Try this:

DeleteCases[test, "", 2]

>, <

Since this is about a list of associations, the level on which to search the pattern "" is level 2 (only), therefore the 2 as third argument.

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

Try this:

DeleteCases[test, "", 2]

>, <

Since this is about a list of associations, the level on which to search the pattern "" is level 2 (only), therefore the 2 as third argument.

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

edited Sep 9 at 17:41

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

answered Sep 9 at 17:01

Henrik Schumacher

37.5k249107

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

add a commentÂ |Â

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

Ahh... that makes sense. My earlier attempts didn't take into consideration the level of the key and value.
â€“Â kickert
Sep 9 at 17:20

add a commentÂ |Â

up vote
6
down vote

Select:

Select[# != "" &] /@ test

"A" -> 1, "B" -> 2

DeleteMissing:

DeleteMissing[test /. "" -> Missing, 2]

<

AssociationMap:

AssociationMap[If[#[[2]] == "", Nothing, #] &] /@ test

>

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

2

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

add a commentÂ |Â

up vote
6
down vote

Select:

Select[# != "" &] /@ test

"A" -> 1, "B" -> 2

DeleteMissing:

DeleteMissing[test /. "" -> Missing, 2]

<

AssociationMap:

AssociationMap[If[#[[2]] == "", Nothing, #] &] /@ test

>

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

2

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

add a commentÂ |Â

up vote
6
down vote

Select:

Select[# != "" &] /@ test

"A" -> 1, "B" -> 2

DeleteMissing:

DeleteMissing[test /. "" -> Missing, 2]

<

AssociationMap:

AssociationMap[If[#[[2]] == "", Nothing, #] &] /@ test

>

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

Select:

Select[# != "" &] /@ test

"A" -> 1, "B" -> 2

DeleteMissing:

DeleteMissing[test /. "" -> Missing, 2]

<

AssociationMap:

AssociationMap[If[#[[2]] == "", Nothing, #] &] /@ test

>

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

edited Sep 9 at 19:17

answered Sep 9 at 17:17

kglr

159k8184384

answered Sep 9 at 17:17

kglr

159k8184384

answered Sep 9 at 17:17

kglr

159k8184384

2

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

add a commentÂ |Â

2

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

For some of my more complicated datasets, this actually provides me with even more functionality. Thanks for the suggestion.
â€“Â kickert
Sep 9 at 17:21

add a commentÂ |Â

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