Sorry for the newbie question so i have an array as code below:
import numpy as np
p = np.array([[2,3,0,5],[2,3,4,5],[2,3,4,5],[0,0,0,0]])
p[np.where(p[0]==0)]=100
print(p)
I wanted to change the first rows 0th value to be 100. However the output is:
[[ 2 3 0 5]
[ 2 3 4 5]
[100 100 100 100]
[ 0 0 0 0]]
So it was changing the 3rd row. A bit perplex. Can I use where? What are other suggestions.
Kevin
[[2 3 100 5]
[2 3 4 5]
[2 3 4 5]
[0 0 0 0]]
Directly use indexing:
p[0, p[0]==0] = 100
Updated p:
array([[ 2, 3, 100, 5],
[ 2, 3, 4, 5],
[ 2, 3, 4, 5],
[ 0, 0, 0, 0]])
Related
I have a 2D array of form
[[ 1 6]
[ 2 7]
[ 5 6]
[ 6 1]
[ 6 5]
[ 7 2]]
I want the output of the form
[[ 1 6]
[ 2 7]
[ 5 6]]
How I can get this output?
Here's a solution using plain Python, but I'm sure there's a more idiomatic way with NumPy.
import numpy as np
a = np.array([
[1, 6],
[2, 7],
[5, 6],
[6, 1],
[6, 5],
[7, 2]])
seen = set()
out = []
for row in a:
elements = frozenset(row)
if elements not in seen:
seen.add(elements)
out.append(row)
print(np.array(out))
Output:
[[1 6]
[2 7]
[5 6]]
I have an array with the shape (10000,6). For example:
a = np.array([[5, 5, 5, 5, 5, 5][10, 10, 10, 10, 10][15, 15, 15, 15, 15]...])
I want to take every 25th array and subtract its element values from the next 25 elements until a new subtraction array in selected. so for example if the first array is:
[10, 10, 10, 10, 10]
then these values should be subtracted on the array itself and the next 25 arrays until for example a new subtraction array like this is selected:
[2, 2, 2, 2, 2]
then the array itself and the following 25 elements should be subtracted that arrays values.
This means that after the operation every 25th array will be:
[0, 0, 0, 0, 0]
because it has been subtracted by itself.
Here's what I would do:
import numpy as np
arr = np.random.randint(0, 10, (9, 3))
group_size = 3
# select vectors you want ot subtract and copy them {group_size} times
selected = arr[::group_size].repeat(3, axis = 0)
# subtract selected vectors from all vectors in the group
sub_arr = arr-selected
output:
arr =
[[9 6 3]
[8 3 3]
[2 0 4]
[0 3 9]
[3 9 9]
[0 8 6]
[4 0 0]
[6 1 9]
[2 6 4]]
selected =
[[9 6 3]
[9 6 3]
[9 6 3]
[0 3 9]
[0 3 9]
[0 3 9]
[4 0 0]
[4 0 0]
[4 0 0]]
sub_arr =
[[ 0 0 0]
[-1 -3 0]
[-7 -6 1]
[ 0 0 0]
[ 3 6 0]
[ 0 5 -3]
[ 0 0 0]
[ 2 1 9]
[-2 6 4]]
You can reshape your array so that each chunk has the right number of lines, and then simply subtract the first line
import numpy as np
a = np.arange(10000)[:, None] * np.ones(6)
a = a.reshape(-1, 25, 6)
a -= a[:, 0, :][:, None, :]
a = a.reshape(-1, 6)
i want to make a list by combining the results of n. but when the x values are different, it creates a new list. However, if the x value is the same, it will be in 1 list
My code is like this
muy = [[1,2,3],[4,5,6],[7,8,9]]
# will = []
for x in muy:
for y in muy:
if x != y:
print(x, " ", y)
m = np.subtract(x, y)
n = sum(m)
print(m)
print(n)
the result is like this
[1, 2, 3] [4, 5, 6]
[-3 -3 -3]
-9
[1, 2, 3] [7, 8, 9]
[-6 -6 -6]
-18
[4, 5, 6] [1, 2, 3]
[3 3 3]
9
[4, 5, 6] [7, 8, 9]
[-3 -3 -3]
-9
[7, 8, 9] [1, 2, 3]
[6 6 6]
18
[7, 8, 9] [4, 5, 6]
[3 3 3]
9
the result what i want is like this:
[[-9,-18][9,-9][18,9]]
what should i do?
muy = [[1,2,3],[4,5,6],[7,8,9]]
will = []
for x in muy:
temp = []
for y in muy:
if x != y:
m = np.subtract(x, y)
n = sum(m)
temp.append(n)
will.append(temp)
print(will)
I need to make a sequence of an array with different length by reading a dataset. I need to call each of them in a loop so probably I need some sort of indexing in order to call them. For example, how can I create the following sequence:
P[1]=[1 2 3 4]
P[2]=[1 4]
P[3]=[8 9 0 0 5 6]
.
.
.
Here it is:
julia> P = Vector{Vector{Int64}}([[1,2,3,4],[1,4],[8,9,0,0,5,6]])
3-element Array{Array{Int64,1},1}:
[1, 2, 3, 4]
[1, 4]
[8, 9, 0, 0, 5, 6]
julia> P[1]
4-element Array{Int64,1}:
1
2
3
4
julia> P[2]
2-element Array{Int64,1}:
1
4
julia> P[3]
6-element Array{Int64,1}:
8
9
0
0
5
6
If you want to add a new element use push!():
julia> push!(P,[7,8,9])
4-element Array{Array{Int64,1},1}:
[1, 2, 3, 4]
[1, 4]
[8, 9, 0, 0, 5, 6]
[7, 8, 9]
I want to compare the current element inside an iteration to the rest of the elements in the array. I have no issues from the starting point. The issue comes when I am looking to compare the current element to the elements behind it inside the array.
array = [1, 2, 3, 2, 3, 4, 5]
array.each_with_index do |num, index|
break if array[index + 1] == nil
if num > array[index + 1]
puts "#{num} is greater than the #{array[index + 1]}!"
else
puts "#{num} is less than the #{array[index + 1]}!"
end
end
I am looking for something like:
"3 is greater than 1 and 2 but less than 4 and 5"
Any ideas?
I'm assuming you want all of the elements in the array compared, so you could do something like the following, by making use of Array#select:
array = [1, 2, 3, 2, 3, 4, 5]
filtered_array = array.uniq
array.each do |i|
greater_than = filtered_array.select { |comp| comp < i }
less_than = filtered_array.select { |comp| comp > i }
puts "#{i} is greater than #{greater_than} but less than #{less_than}"
end
You could play with formatting the output, but this would give:
1 is greater than [] but less than [2, 3, 4, 5]
2 is greater than [1] but less than [3, 4, 5]
3 is greater than [1, 2] but less than [4, 5]
2 is greater than [1] but less than [3, 4, 5]
3 is greater than [1, 2] but less than [4, 5]
4 is greater than [1, 2, 3] but less than [5]
5 is greater than [1, 2, 3, 4] but less than []
partition breaks divides up the elements into two separate groups.
array = [1,2,3,4,5]
array.each do |n|
less_than, greater_than = *(array - [n]).partition { |m| m <= n }
text = []
text << "is greater than #{less_than.join(', ')}" if less_than.count > 0
text << "is less than #{greater_than.join(', ')}" if greater_than.count > 0
puts "#{n} #{text.join(' and ')}"
end
arr = [1, 2, 3, 2, 3, 4, 5]
a = arr.uniq.sort
#=> [1, 2, 3, 4, 5]
h = a.each_with_index.to_h
#=> {1=>0, 2=>1, 3=>2, 4=>3, 5=>4}
arr.each { |i| puts "#{i} is greater than #{a[0,h[i]]} but less than #{a[h[i]+1..-1]}" }
prints
1 is greater than [] but less than [2, 3, 4, 5]
2 is greater than [1] but less than [3, 4, 5]
3 is greater than [1, 2] but less than [4, 5]
2 is greater than [1] but less than [3, 4, 5]
3 is greater than [1, 2] but less than [4, 5]
4 is greater than [1, 2, 3] but less than [5]
5 is greater than [1, 2, 3, 4] but less than []