How to find magnitude of an array of 17 vectors

I have imported a txt file and need to find the magnitude of the 17 vectors on the file. Thanks.

Answer 1

[madhan ravi]

Use :

norm(x) %x - is a vector, norm syntax calculates the magnitude of the vector

*AN EXAMPLE: *

X= rand(10,10)

size(X)

for i = 1:length(X)

      MAG(i,:) = norm(X(i,:)); %calculates the magnitude of 10 vectors separately in each iteration

end

MAG

size(MAG)

[Sarah Hicks]

I keep getting the same magnitude for all 17 vectors, and that should not be the case. Is there something you think I am doing wrong?

A=(17,2) i=1:length(A) MAG(i,:)=norm(A(i,:))

It gives me 17 separate magnitudes, but they are all the same number x.

[madhan ravi]

can you upload A?

[madhan ravi]

Is it just a number or what? I don't understand.

[madhan ravi]

vector is something like => vector=[1 4 5 7 8]

[madhan ravi]

DATAS=load('lamelli.txt')
X=DATAS
size(X)
for i = 1:length(X)
      MAG(i,:) = norm(X(i,:)); 
end
MAG
size(MAG)

[Sarah Hicks]

Thank you so much. This is my first encounter with MATLAB so I was very unsure how to use it.

[madhan ravi]

if you find it useful please accept the answer

[Image Analyst]

Length() gives the longest dimension. I don't think it's a good idea to use it on a matrix. I use it only on vectors. For some reason the lamelli.txt file got removed from the post. If it's only 2 or 3 columns, it should be okay but if it has more than 17 columns, there will be a problem. Plus you shouldn't use i as a loop index, and you don't need a second dimension for MAG. To be more robust, here is how I'd do it:

data = load('lamelli.txt')
[rows, columns] = size(data)
magnitudes = zeros(rows, 1); % Preallocate
for k = 1: rows
  magnitudes(k) = norm(data(k,:));
end
magnitudes      % Print to command window.
whos magnitudes % Print info to command window.

[madhan ravi]

Thank you @sir Image Analyst much appreciated.

Answer 2

[Steven Lord]

If you're using release R2017b or later, use the vecnorm function to compute the norm of vectors stored in an array.

Answer 3

[Joshua Daniels]

sqrt(sum(data.^2,dim)) where dim is the dimention that your vectors are written in. ie a 5x3 vertical list of horizontal vectors would use dim=2 since each vector is in the horizontal dimention.