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how to exclude null values in array_agg like in string_agg using postgres?
... non_canonical_users
FROM groups g
GROUP BY g.id
) s
Or, simpler and may be cheaper, using array_to_string which eliminates nulls:
SELECT
g.id,
array_to_string(
array_agg(CASE WHEN g.canonical = 'Y' THEN g.users ELSE NULL END)
, ','
) canonical_users,
array...
Typedef function pointer?
I'm learning how to dynamically load DLL's but what I don't understand is this line
6 Answers
...
Is there a function to make a copy of a PHP array to another?
...ike an array. Being an object however, it has reference semantics.
Edit: @AndrewLarsson raises a point in the comments below. PHP has a special feature called "references". They are somewhat similar to pointers in languages like C/C++, but not quite the same. If your array contains references, then...
Converting JSON String to Dictionary Not List
I am trying to pass in a JSON file and convert the data into a dictionary.
6 Answers
6...
Creating an R dataframe row-by-row
...d like to construct a dataframe row-by-row in R. I've done some searching, and all I came up with is the suggestion to create an empty list, keep a list index scalar, then each time add to the list a single-row dataframe and advance the list index by one. Finally, do.call(rbind,) on the list.
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How do I convert a numpy array to (and display) an image?
...
You could use PIL to create (and display) an image:
from PIL import Image
import numpy as np
w, h = 512, 512
data = np.zeros((h, w, 3), dtype=np.uint8)
data[0:256, 0:256] = [255, 0, 0] # red patch in upper left
img = Image.fromarray(data, 'RGB')
img.sa...
What are advantages of Artificial Neural Networks over Support Vector Machines? [closed]
ANN (Artificial Neural Networks) and SVM (Support Vector Machines) are two popular strategies for supervised machine learning and classification. It's not often clear which method is better for a particular project, and I'm certain the answer is always "it depends." Often, a combination of both alon...
Print new output on same line [duplicate]
...
Thanks for the quick response and update. That makes so much more sense now. I read the help function a dozen times and wasn't obviously paying attention. :)
– onxx
Aug 20 '12 at 4:39
...
Where is C not a subset of C++? [closed]
...definitions in C++
int n;
int n; // ill-formed: n already defined
int[] and int[N] not compatible (no compatible types in C++)
int a[1];
int (*ap)[] = &a; // ill-formed: a does not have type int[]
No K&R function definition style
int b(a) int a; { } // ill-formed: grammar error
Nest...
Can lambda functions be templated?
...
UPDATE 2018: C++20 will come with templated and conceptualized lambdas. The feature has already been integrated into the standard draft.
UPDATE 2014: C++14 has been released this year and now provides Polymorphic lambdas with the same syntax as in this example. Some...