Questions tagged [query]

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4
votes
1answer
70 views

How can default valued be added in a Query?

I'm not understanding the the default values are not used to produced a length of 0 in the following example. What is the right way to add default values during a query? ...
0
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0answers
59 views

Transforming a time-series Dataset

I am trying to perform some analysis on a Dataset instance but my 28K queries involve a Select[#MAC==mac&] over the whole ...
0
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0answers
17 views

How to specify authenticity of SSL for querying APIs?

While ago I was using this command with no issue, now I have an SSL error: ...
4
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2answers
129 views

Select dataset rows that meet a mathematical criterion in a column

Here is a simple dataset: ...
9
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1answer
139 views

Generating Google BigQuery API Access Token in Wolfram Language

I'm working on a Wolfram Language Package to connect into Google Bigquery (that I'll make public available). In order to finish It, I need to solve a last step, that is how to get an authentication ...
4
votes
2answers
109 views

Using subquery in Query of Dataset

I want to create a Query to a Dataset that will select a subset of three columns, modify the date column in this subset (to month), group by month and a second column (location), take the group means ...
5
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1answer
153 views

How can I understand this example of Query taken from current Mathematica documentation?

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2
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0answers
54 views

Is there a documented meaning for the following Query syntax?

Consider this example: ...
2
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0answers
71 views

Efficiently get positions of Query results

I have some very large Datasets. Is there any efficient method of getting the positions of results found in a Query? That is, without using ...
4
votes
1answer
69 views

A simple way to extract information from this dataset with Query?

I have a dataset comparable to the following (you may wrap it in Dataset if you like). I am looking for a relatively simple way to query it and extract information. ...
0
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0answers
31 views

Can the following operation be performed in a single query without using explicit Maps or nesting Queries?

Is there a way to include the function StringPosition["e"] inside the Query in the following: ...
1
vote
1answer
65 views

A more efficient way to interrogate data inside a Dataset: a generic relational map

I have a Dataset that stores the relationships between people IDs (in columns) and the events they attended (in rows). I want to produce a linear text report of those relationships. How can I do this ...
13
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2answers
336 views

Does anyone know a way to use patterns in Query?

This question is a follow up from my previous question. Query has a nice syntax that allows it to apply functions on association based on specific ...
3
votes
3answers
681 views

Select specific rows of a dataset

I am struggling with extracting specific rows from a dataset. ...
7
votes
2answers
257 views

How does Query decide the order in which the functions are applied?

First of all I know that Query is a nice way to organize your functions that are applying at specific levels of an expression. But I don't understand the order in ...
0
votes
1answer
152 views

Using Semantic Import to do an Excel-like VLookUp using Mathematica

I'm following an example provided in the following Stack Exchange Link but, using a different approach. My data is contained in an Excel workbook called "Input Workbook.xlsx" as shown here: I ...
0
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1answer
115 views

What is the analog of Query in python? [closed]

Is there an analog of Query[] in Python 3.8+?
4
votes
1answer
80 views

Inconsistency in getting Keys, Values and Query for nested Rules

Querying nested Rule expressions of the form a -> v -> b // FullForm Rule[a,Rule[v,b]] for ...
4
votes
2answers
116 views

How to pull out the underlying query syntax being used by dataset?

Consider the following dataset. titanic = ExampleData[{"Dataset", "Titanic"}] If I use the lookup syntax of the dataset like following it creates an equivalent <...
8
votes
2answers
175 views

Query inside Dynamic triggers continuous high CPU load for FE

Here is a (vicious) problem I am able to reproduce with v12 and v11.3 (previous versions not tested) and OSX. This is a minimal example to demonstrate it (even if it seems useless here I do need <...
1
vote
0answers
47 views

How do I Select when the key of an association is a multi-word string [closed]

I have imported some survey responses into a Dataset. I now want to select those rows where the response to "participant type" == "Virtual". I discovered that this ...
4
votes
2answers
88 views

Simple dataset query

Why does taking a Part fail in a Dataset query function when there is an operation in the index argument? ...
2
votes
1answer
141 views

Replacing values in a dataset

Could someone explain why ...
0
votes
1answer
160 views

Aggregate function problem

I use a function to do something similar to a SQL sum. I've asked about simplifying it in another post. I'm still using this function and it works well for aggregates like ...
4
votes
1answer
83 views

Operator form for Histogram of multiple datasets?

I would like to plot a histogram for multiple datasets in a dataset query, but can't quite seem to make it work in operator notation: ...
2
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0answers
35 views

Keyed eigensystem for nested Association

Suppose a matrix is given where both rows and columns are keyed, for example this correlation matrix: ...
2
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1answer
64 views

Handling Missing values flexibly in Query (MissingBehavior problem)

There’s an inconsistency in how Missing values are imputed in Query, with ...
6
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1answer
308 views

How to filter this nested list of Association

For example, I have the following data ...
3
votes
1answer
140 views

Query from Association of Associations Dataset

I have a rather large dataset comprised of Association of Associations. For better or worse, I've converted this into a Dataset. Here is a simplified version of ...
7
votes
3answers
303 views

Applying a function by Key pattern, preserving Association order

Any convenient ways to apply a function to Keys that match a pattern in an Association? Method should handle: Mixture of ...
8
votes
1answer
85 views

Unexpected behavior of PreIncrement when querying associations

For reasons I won't go into here, I became curious about the what would happen should I make a query that applies PreIncrement to one key in a list of associations....
4
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0answers
105 views

How to get parent key in Query on Association/Dataset?

Is there a general and terse method to obtain the parent key of the current "position" in a Query of an Association/...
4
votes
2answers
34 views

How to Quiet an operator to avoid Query fail

This Query fail, due to divide by zero error message... <|"a" -> 1, "b" -> 0|> // Query[#a/#b &] Missing["Failed"] ...can be prevented by ...
8
votes
1answer
389 views

Transpose fail in 11.1 Dataset

The type system underlying Dataset seems a total kludge, as soon as one issue is fixed, here it recurs in a slightly different form - and difficult to isolate in minimal examples. Here's a failure ...
3
votes
1answer
82 views

Dataset type system fail with composite keys and Infinity

In 11.1, a Dataset consisting of an Association with composite keys with an Infinity causes failure in keying-in: ...
9
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2answers
187 views

Getting slices of a nested Association via Query

I'd like to get specific slices from a nested database-like Association through Query. Take for example this toy database of ...
3
votes
2answers
141 views

Composition with Transpose failure with Dataset

Is the failure of the 2nd Transpose here a known bug? Dataset[{{0, 10}, {2, 11}, {3, 12}}][ Transpose /* Map[MinMax] /* Transpose] // Normal ...
11
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2answers
267 views

Simplifying a reverse Fold for a Query

Is there a simpler way to parametrize this tail-recursive expression to be applied as a Query (for processing a nested ...
9
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2answers
247 views

Slicing an Association with named key span without normalizing?

Is there way to slice an Association with named key span? Span currently doesn't accept named keys: ...
21
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2answers
384 views

Query: adding additional operator changes meaning of preceding operators

Consider the following query: Range[5] // Query[Select[EvenQ] /* Append[1], f] (* {f[2], f[4], 1} *) It selects the even numbers, applies ...
3
votes
0answers
64 views

Aligning input form of a sequence of Queries

Is there a way to modify the parser, or define options, to align the indentation of a sequence of Queries on a Dataset? Given: ds = <|"a" -> 1, "b" -> <|"c" -> 2|>, "d" -> <|"e" -> 3, "f" ...
12
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0answers
175 views

Unix-like reference to parent and root Association?

Is there a syntax or function to reference parent and root when querying nested Associations similar to Unix' ".." and "/", eg "cd ../../mydir". ? Here's a typical application of the root construct....
2
votes
1answer
278 views

Query and Dataset Syntax Peculiarities

Question Can someone please explain to me the syntax of Query and why its behavior is so befuddling to me at the moment? I am going to go through a few simple ...
11
votes
2answers
208 views

Large Dataset query fails if column contains Missing

In version 11.0 (Win 8.1 Pro) a query on a large Dataset for a column that contains Missing fails most unceremoniously. With <...
4
votes
1answer
178 views

Passing values from a list to Select during a Dataset query

Given a Dataset: ...
6
votes
1answer
117 views

Mapping (Query) a function at multiple locations in nested data via All, Span

For this data: dt = <|"a"-> <|"x"-> 1|>,"b"-> <|"y"-> 2|>,"c"-> <|"z"->3|>|> It’s awkward when mapping the same ...
11
votes
2answers
190 views

A subtlety in Query

Let us consider a simple Dataset: ds=Dataset[{<|"a"->12,"b"->4|>,<|"a"->7,"b"->8|>,<|"b"->3|>}] Column "b" is easy to find: <...
6
votes
2answers
140 views

Nothing in a Query

In Mathematica 10, Nothing is defined as to automaticaly disappear when used in a list or in an association, and moreover with the property that it returns ...
17
votes
1answer
282 views

Aggregation queries on lists of associations in 10.3

Bug introduced in 10.3.0 and fixed in 10.3.1 Bug introduced in 10.3.0 and fixed in 10.4.0 First bug, see first part of the question Second bug, see update part Some aggregation queries applied to ...
23
votes
1answer
610 views

Struggling to understand Query

The documentation for Query starts with: ...