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I try vectorizing a 'for loop' for array but it does not work to me.
My 'for loop' is
for k = 1:N
R(n,n,k) = R(n,n,k) - SE3(k,k);
end
and vectorize it
diagSE3 = diag(SE3);
R(n,n,1:N) = R(n,n,1:N) - diagSE3(1:N);
With
R(n,n,1:N) = R(n,n,1:N) - diagSE3(1:N)
you try to subtract a vector (N x 1) from a 3-dimensional array with dimensions 1 x 1 x N. This can be repaired using squeeze:
R(n,n,1:N) = squeeze(R(n,n,1:N)) - diagSE3(1:N)
Related
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How do I swap an(example) array's second and third elements? I tried the following
def swap_elements(array)
array = ["blake", "ashley", "scott"]
array[1], array[2] = array[2], array[1]
end
but I get
: ["scott", "ashley"]
I lost the first[0] element
There are many ways to do this - this is a functional approach that doesn't mutate the original array:
def swap_elements(array)
# yields the array to the block
array.then do |first, *rest| # deconstruct the array
rest.reverse # swap the places of 2 & 3
.unshift(first) # put the first back in
end
end
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What does it mean in MATLAB when I do:
array = array (1:number)
and what does it mean:
array = array(indexes_array)
and finally, what does it mean:
array = array(indexes_array,:)
Answers, according to MATLAB docs:
1)
array = array (1:number)
The colon notation in MATLAB provides an easy way to extract a range of elements from v:
v(3:7) % Extract the third through the seventh elements
ans =
9 4 2 11 7
2)
array = array(indexes_array)
array is reorganized according to indexes_array order, assuming that indexes_array is composed of indexes.
3)
array = array(indexes_array,:)
just the same as number 1), array is reorganized according to all the rows of indexes_array, ignoring the columns.
References:
https://www.mathworks.com/help/matlab/math/array-indexing.html
https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html
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S.a=rand(100,3)
S.b=rand(100,3)
S.c=rand(100,3)
S.d=rand(100,3)
K.a=[ ]
K.b=[ ]
K.c=[ ]
K.d=[ ]
for i=1:numel(S)
if rand<0.8 % condition
K(i,:)=S(i,:) % How this assignment can be made
end
end
How to extract the rows of all the fields of a structure and store it to another structure.
I'm not entirely sure from you explanation if this is what you want. The following code will copy the fields from in S into K for just the rows where the items are < 0.8
S.a=rand(100,3);
S.b=rand(100,3);
S.c=rand(100,3);
S.d=rand(100,3);
K = [];
for field = ['a', 'b', 'c', 'd']
I = rand(length(S.(field)), 1) < 0.8;
K.(field) = S.(field)(I,:);
end
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Leonardo number
L(x)= {
1 if x=0
1 if x=1
L(x-1)+L(x-2)+1 if x>1
}
If x>1, what logic can I apply to find out the Leonardo number?
In your function L(int x)
If x is 0 or 1
return 1;
If x is greater than 1
return L(x-1) + L(x-2) + 1;
What I am doing using L(x - 1) is calling the function for the value x - 1 and the value will be evaluated directly as 1 if it is 0 or 1, otherwise it call again for (x - 1) - 1 i.e. x - 2 and the process repeats.
Same is the case for calling L(x - 2).
This is the logic, without the entire code.
For more information on this kind of logic, try searching for Recursion.
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I have 2 arrays of strings as under. I want to compare them and execute some code if these arrays are not equal-
current_instances = ["170601_7711", "170601_8811"]
app_instances = ["170602_7711", "170602_8811"]
How can I compare them in ruby?
x = ["alpha1", "beta1"]
y = ["alpha2", "beta2"]
Check if all elements are the same
x == y #=> false
Compare each element
Compare each string at some index i, assuming both arrays are the same size. Then apply some code to the matches.
x.zip(y) #=> [["alpha1", "alpha2"], ["beta1", "beta2"]]
x.zip(y).map {|a,b| a == b ? 'do this' : 'else do this' }
#=> ["else do this", "else do this"]
Perhaps you can do an array difference with the - operator and execute your code if the difference is zero
arr_diff = current_instances - app_instances
This is the simplest solution I could think of :)
Check my solution and let me know how it goes