pdist | Calculate mean of pairwise weighted distances | Machine Learning library
kandi X-RAY | pdist Summary
kandi X-RAY | pdist Summary
Calculate the mean of the pairwise weighted distances between points using the great circle metric :globe_with_meridians: for a very big dataset without running out of RAM :bomb: and/or waiting till the end of the universe. :joy:.
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QUESTION
I have a large Dataframe (189090, 8), I need to calculate Euclidean distance and the similarity.
My approach:
...ANSWER
Answered 2022-Mar-09 at 10:54According to the documentation, pdist "returns a condensed distance matrix". That means it would try to calculate and return a matrix of about 189090^2/2 = 17877514050 entries, causing your computer run out of ram.
If you want to calculate distances between some specific data points, filter them out before using pdist.
If you really want to calculate the entire distance matrix, it's better to calculate distances of a small partition of data points at a time (e.g. 1000), and save the result in the disk.
QUESTION
I have a dataset constructed as a sparse weighted matrix for which I want to calculate weighted Jaccard index for downstream grouping/clustering, with inspiration from below article: http://static.googleusercontent.com/media/research.google.com/en//pubs/archive/36928.pdf
I'm facing a slight issue in finding the optimal way for doing the above calculation in Python. My current function to test my hypothesis is the following:
...ANSWER
Answered 2022-Feb-27 at 15:03You can use concatenate:
QUESTION
I have a data frame with shape:
...ANSWER
Answered 2022-Feb-07 at 14:54The most straightforward way to reshape that I can think of, according to how you described the problem, is:
QUESTION
I have a dendrogram calculated from some data points labeled 0-9.
How do I retrieve which datapoints (0-9) are in each node from the output of scipy.cluster.hiearchy.dendrogram
? I want to label each node by its average (x,y) value.
I know I can retrieve the clusters using the clustering algorithm (Scikit learn agglomerative clustering for example) but I want to label the whole dendrogram by the average value in each node.
ANSWER
Answered 2022-Feb-01 at 11:24You can use the leaf_label_func
parameter.
QUESTION
Thank you for reading this. Currently I have a lot of latitude and longitude for many locations, and I need to create a matrix of distances for locations within 10km. (It's okay to fill the matrix with 0 distances between locations far more than 10km).
Data looks like:
...ANSWER
Answered 2022-Jan-18 at 14:45First of all, do you need to use haversine
metric for distance calculation? Which implementation do you use? If you would use e.g. euclidean
metric your calculation would be faster but I guess you have good reasons why did you choose this metric.
In that case it may be better to use more optimal implementation of haversine
(but I do not know which implementation you use). Check e.g. this SO question.
I guess you are using pdist
and squareform
from scipy.spatial.distance
. When you look at the implementation that is behind (here) you will find they are using for loop. In that case you could rather use some vectorized implementation (e.g. this one from the linked question above).
QUESTION
I am comparing the Jaccard distance matrix I get when I process a dataset using pdist
and a DIY Jaccard distance matrix function. I'm getting different results in my output distance matrices and I'm not sure why.
I think one of the following is the cause:
- My implementation of jaccard distance calculation is wrong
scipy.spatial.distance.pdist
(metric = 'jaccard')
andscipy.spatial.distance.jaccard
calculate jaccard distance in different ways (seems unlikely as their both inscipy.spatial.distance
)squareform
is doing something to my data, potentially a normalisation
The docs for squareform go a bit over my head so some form of normalisation might be what's happening. However, the squareform-ed distance matrix does not have the same relative distance magnitudes between cells which is confusing (e.g. row 0 in my DIY distance matrix is 0, 0.571429, 1
, and with pdist
is 0, 1, 1
- the middle value is twice as high with pdist
).
Can anyone explain the why I'm getting a different distance matrix when it's being analysed with the same metric?
My code:
...ANSWER
Answered 2022-Jan-03 at 11:26Looks like pdist
considers objects at a given index when comparing arrays, rather than just what objects are present in the array itself - if I change data_array[1]
to 3, 4, 5, 4, 5
then the distance matrix changes to reflect the fact that data_array[0][3:5] == data_array[1][3:5]
:
QUESTION
from scipy.spacial.distance import squareform, pdist, cdist
...ANSWER
Answered 2021-Dec-26 at 21:58After some searching, I found out that scipy.spatial.distance
is the correct spelling of the Module. Did you try import that?
QUESTION
This question: Numpy where function multiple conditions asks how to use np.where
with two conditions. This answer suggests to use the &
operator between conditions, which works if we have a low number of conditions which can be typed. This answer suggests using the np.logical_and
, which can take only two arguments.
This thread: Numpy "where" with multiple conditions also discusses multiple conditions for np.where
, but the number of conditions are known in advance.
I am looking for a way to evaluate an np.where
expression without knowing the number of conditions in advance.
I have a 2D array:
...ANSWER
Answered 2021-Dec-09 at 13:07Tried to avoid eval. It has some security implications.
You could to it iteratively, like so
QUESTION
I have 2 classes in model and I would like to validate that value in a field from one class is smaller than field from second class. I went through Fluent documentation but I cannot find a real example.
...ANSWER
Answered 2021-Oct-24 at 00:50Assuming that you're using the latest version of FV, and there is no way to establish a relationship between the models, I'd normally tackle this using RootDataContext. You haven't stated how you're invoking your validators, however this method becomes a server side invocation - you'll need to invoke the validator manually as you need to populate the root data context dictionary.
Provided the above suits, then start by adding a rule:
QUESTION
sorry for my bad english. I am trying to compare two faces using python3 module 'face_recognition'
here is an example of calculating euclidean distance in python
pdist([vector1, vector2], 'euclidean')
I want to calculate euclidean distance only in SQL query, because all faces(theirs vectors) will be stored in my database, but I do not know how to do this with a SQL query.
Information:
MariaDB version: 10.5.11
Python: 3.9.2
...ANSWER
Answered 2021-Oct-17 at 17:26Here is what you need!
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