Group Abstract Group Abstract

Message Boards Message Boards

1
|
15.1K Views
|
6 Replies
|
9 Total Likes
View groups...
Share
Share this post:

Missing["KeyAbsent", somekey] (How to extract somekey)?

Caitlin Ramsey
Posted 11 years ago

Hello, I am using the KeyUnion function to combine a couple of lists of lists. In some cases, a key exists in one list of sublists, but not in the other.

Here is an example: 

assoc1 = <|1 -> {1, a, aa},3 -> {3, c, cc}|>

assoc2 = <|1 -> {1, 10, 100, 1000}, 5 -> {5, 50, 500, 5000}|>

I do a KeyUnion.... 

assocList = KeyUnion[{assoc1, assoc2}]

...to get something like this...

assocList = { <|1 -> {1, a, aa},3 -> {3, c, cc}, 5 -> Missing["KeyAbsent", 5]|>, <|1 -> {1, 10, 100, 1000},  
     3 -> Missing["KeyAbsent", 3], 5 -> {5, 50, 500, 5000}|>}

Now I want to merge the two lists, based on the key, replacing the missing values by some Key, Value pair that includes "dummy" value such as 5->{-9999}. The following piece of code, for example, works nicely for an individual replacement (eg. Key "3"):

Merge[{assocList[[1]], assocList[[2]]}, Identity]
merged = Values[%] /. _Missing -> {3, -9999};

To get... 

{{{1, a, aa}, {1, 10, 100, 1000}}, {{3, c, cc}, {3, -9999}},...}

But you also get...

 {...,{{3,-9999}, {5, 50, 500, 5000}},...}

Which is not what we want. (The ultimate goal is to make a Union between the two lists associated with each key, where the first item in the list is also the same as the key.)

What I am looking for is a way to make a {Key, Value} pair replacement for each missing key. Is there a way to Is there a way to pick out the "index" part of the Missing[KeyAbsent, index] so that I can write a replacement rule that iterates over the keys?
POSTED BY: Caitlin Ramsey
6 Replies
Sort By:
Caitlin Ramsey
Caitlin Ramsey
Posted 11 years ago

Yes, please do. The source is not confidential. I am attaching a text file.

Attachments:
POSTED BY: Caitlin Ramsey

Not much to do with this. I loaded the file down to the local machine and could open it with MS Excel but

In[15]:= dS = SemanticImport[FileNameJoin[{NotebookDirectory[], "others", "ramsey", "timeseries_fy14.csv"}]]
Out[15]= $Failed

In[16]:= FileNameJoin[{NotebookDirectory[], "others", "ramsey", "timeseries_fy14.csv"}]
Out[16]= "N:\\Udo\\Abt_N\\others\\ramsey\\timeseries_fy14.csv"

In[22]:= FileNames[FileNameJoin[{NotebookDirectory[], "others", "ramsey", "*"}]]
Out[22]= {"N:\\Udo\\Abt_N\\others\\ramsey\\Example_Missing.txt", \
          "N:\\Udo\\Abt_N\\others\\ramsey\\timeseries_fy14.csv"}

In[18]:= sales = SemanticImport["ExampleData/RetailSales.tsv"]
Out[18]= $Failed

SemanticImport has a denial of service, even with the example from the help (RetailSales.tsv). Is the user supposed the preprocess the file before SemanticImport?

In[25]:= Clear[dS]
dS = SemanticImport[FileNameJoin[{NotebookDirectory[], "others", "ramsey", "timeseries_fy14.csv"}],
  Automatic, "Rows", "CharacterEncoding" -> "Unicode", HeaderLines -> 1]
Out[26]= $Failed
POSTED BY: Udo Krause
Caitlin Ramsey
Caitlin Ramsey
Posted 11 years ago
POSTED BY: Caitlin Ramsey
POSTED BY: Udo Krause

This

    In[37]:= Clear [assoc1, assoc2]
    assoc1 = <|1 -> {1, a, aa}, 3 -> {3, c, cc}|>;
    assoc2 = <|1 -> {1, 10, 100, 1000}, 5 -> {5, 50, 500, 5000}|>;

    In[41]:= assocList = KeyUnion[{assoc1, assoc2}, <|1 -> {1}, 3 -> {3}, 5 -> {5}|>]
    Out[41]= {<|1 -> {1, a, aa}, 3 -> {3, c, cc}, 5 -> {5}|>,
              <|1 -> {1, 10, 100, 1000}, 3 -> {3}, 5 -> {5, 50, 500, 5000}|>}

    In[44]:= Merge[assocList, Identity]
    Out[44]= <|1 -> {{1, a, aa}, {1, 10, 100, 1000}}, 3 -> {{3, c, cc}, {3}}, 5 -> {{5}, {5, 50, 500, 5000}}|>

does not help? From the manual for KeyUnion:

The missing function can be an association:

the only thing yet to be done is creating the missing function association automatically from the all the present keys which seems possible but now I have to get the gifts out of the wrap ... Merry Christmas everyone!
POSTED BY: Udo Krause

the only thing yet to be done is creating the missing function association automatically

In[19]:= Clear [assoc1, assoc2, assoc3, assoK]
assoc1 = <|1 -> {1, a, aa}, 3 -> {3, c, cc}|>;
assoc2 = <|1 -> {1, 10, 100, 1000}, 5 -> {5, 50, 500, 5000}|>;
assoc3 = <|2 -> {4, 8, 16}, 4 -> {16, 64}, 7 -> {"The", "whole", "nine", "yards"}|>;
assoK = Association @@ (Rule[#, {#}] & /@ Union[Flatten[Keys /@ {assoc1, assoc2, assoc3}]])
Out[23]= <|1 -> {1}, 2 -> {2}, 3 -> {3}, 4 -> {4}, 5 -> {5}, 7 -> {7}|>

In[24]:= Clear[assocList]
assocList = KeyUnion[{assoc1, assoc2, assoc3}, assoK]
Out[25]= {<|1 -> {1, a, aa}, 3 -> {3, c, cc}, 5 -> {5}, 2 -> {2}, 4 -> {4}, 7 -> {7}|>, 
          <|1 -> {1, 10, 100, 1000}, 3 -> {3}, 5 -> {5, 50, 500, 5000}, 2 -> {2}, 4 -> {4}, 7 -> {7}|>, 
          <|1 -> {1}, 3 -> {3}, 5 -> {5}, 2 -> {4, 8, 16}, 4 -> {16, 64}, 7 -> {"The", "whole", "nine", "yards"}|>}

In[26]:= Merge[assocList, Identity]
Out[26]= <|1 -> {{1, a, aa}, {1, 10, 100, 1000}, {1}}, 
           3 -> {{3, c, cc}, {3}, {3}}, 
           5 -> {{5}, {5, 50, 500, 5000}, {5}}, 
           2 -> {{2}, {2}, {4, 8, 16}}, 
           4 -> {{4}, {4}, {16, 64}}, 
           7 -> {{7}, {7}, {"The", "whole", "nine", "yards"}}|>

of course, in defining assoK one could give a value more reminiscent about a missing value like the NULL of SQL ...

POSTED BY: Udo Krause
Reply to this discussion
Community posts can be styled and formatted using the Markdown syntax.
Tag limit exceeded
Note: Only the first five people you tag will receive an email notification; the other tagged names will appear as links to their profiles.
Reply Preview
Attachments
Remove
or Discard