Questions tagged [query]
The query tag has no usage guidance.
60
questions
2
votes
0answers
49 views
2
votes
0answers
50 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
47 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
votes
0answers
30 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
54 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 ...
14
votes
2answers
322 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 ...
2
votes
3answers
166 views
7
votes
2answers
233 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
112 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
votes
1answer
110 views
4
votes
1answer
71 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
109 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
162 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
44 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
70 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
107 views
0
votes
1answer
146 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
69 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
votes
0answers
33 views
Keyed eigensystem for nested Association
Suppose a matrix is given where both rows and columns are keyed, for example this correlation matrix:
...
2
votes
1answer
61 views
Handling Missing values flexibly in Query (MissingBehavior problem)
There’s an inconsistency in how Missing values are imputed in Query, with ...
6
votes
1answer
275 views
3
votes
1answer
118 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
258 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
83 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
votes
0answers
97 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
31 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
356 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
77 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
votes
2answers
176 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
131 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
votes
2answers
247 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
votes
2answers
214 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
votes
2answers
370 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
60 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
votes
0answers
174 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
211 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
198 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
157 views
6
votes
1answer
112 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
187 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
133 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
281 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 ...
20
votes
1answer
550 views
5
votes
2answers
392 views
Remove rows from dataset using query
MyDataSet[Select[#point[Fsr] == 1 &]] returns the row I want to delete, now I am trying what looks to me the most logic command to remove these rows, which is
<...
12
votes
2answers
337 views
Query datasets with “variable” named slots
I want to query a Dataset object, e.g. select some entries using
...
36
votes
1answer
653 views
Visualizing Type System Operations
With the introduction of Dataset in version 10, Mathematica acquired a static type-checking subsystem. A fair number of dataset-related questions here on MSE ...
2
votes
0answers
97 views
Reducing quantile & color map queries for use with Associations [closed]
This set of queries perform basic maps to quantile and then color-map. There's got to be a more compact solution. What are some approaches to reduction?
Numeric:
...
11
votes
1answer
177 views
Preventing Keys from appearing in Query Output (+ the casting of Ascending/Descending operators)
One of the challenges of coming to grips with Query's on Association's and Datasets is ...
2
votes
2answers
403 views
Query in Lists Mathematica - Pivot table
Recently, I finished a simulation, and I got the following data:
...
5
votes
1answer
280 views
Query Dataset to check if row contains any from a set of values
For a given keyless dataset, I can query to return the rows whose columns contain a specific value. For example:
...
