MATLAB: Getting rid of for loop in one-liner code

optimizationvectorization

Lets assume we have an optimization problem like this:

x = zeros(1,10);
x(1,1) = 2;
for k = 1: 9
    x(k+1) = 10 x(k);
end

Is it possible to write the equation without the for loop?

Best Answer

Sakil

ok for a matrix, look:

    A=[1 2;3 4];n=[1:1:10];L=A(:);B=reshape(bsxfun(@power,L,n),[size(A),10])

the resulting exponential matrices are stored in the layers of B

    B(:,:,1) =
         1     2
         3     4
    B(:,:,2) =
         1     4
         9    16
    B(:,:,3) =
         1     8
        27    64
    B(:,:,4) =
         1    16
        81   256
    B(:,:,5) =
               1          32
             243        1024
    B(:,:,6) =
               1          64
             729        4096
    B(:,:,7) =
               1         128
            2187       16384
    B(:,:,8) =
               1         256
            6561       65536
    B(:,:,9) =
               1         512
           19683      262144
    B(:,:,10) =
               1        1024
           59049     1048576

Sakil

would you please be so kind to mark my answer as Accepted Answer,

thanks in advance

regards

John BG

<mailto:jgb2012@sky.com jgb2012@sky.com>

Related Solutions

MATLAB: Build 2-D array with same 1-D array

hi Renuyan

yes, MATLAB has repmat

A=[1 2 3 4 5 4 6]

you set the amount of repetitions

reps=5

to replicate vertically:

repmat(A,reps,1)=
    1.00          2.00          3.00          4.00          5.00          6.00
    1.00          2.00          3.00          4.00          5.00          6.00
    1.00          2.00          3.00          4.00          5.00          6.00
    1.00          2.00          3.00          4.00          5.00          6.00
    1.00          2.00          3.00          4.00          5.00          6.00

replicating horizontally:

repmat(A,1,reps)=
  Columns 1 through 7
 1.00        2.00        3.00        4.00        5.00        6.00        1.00
  Columns 8 through 14
 2.00       3.00         4.00        5.00        6.00        1.00        2.00
  Columns 15 through 21
 3.00       4.00         5.00        6.00       1.00         2.00        3.00
  Columns 22 through 28
 4.00      5.00          6.00        1.00       2.00        3.00         4.00
  Columns 29 through 30
 5.00          6.00

so far the answer, but in similar exercises you may find also useful the command reshape. Let's say you want to stack A, either

reshape(A,[6,1]) =
          1.00
          2.00
          3.00
          4.00
          5.00
          6.00

If you find this answer of any help solving your question, please click on the thumbs-up vote link,

thanks in advance

John

jgb2012@sky.com

MATLAB: Removing maxium and minimum from the matrix

How about this:

format long g
workspace;
D =[...
        100.00          7.80
        200.00          7.50
        300.00          8.50
        400.00          8.40
        500.00         11.10
        600.00         14.50
        700.00         22.60
        800.00         34.90
        900.00         30.00
       1000.00         29.50
       1100.00         21.30
       1200.00         20.50
       1300.00         18.40
       1400.00         15.60
       1500.00         14.00
       1600.00         13.90
       1700.00         13.00
       1800.00         11.80
       1900.00         12.40
       2000.00         13.40
       2100.00          5.60
       2200.00          6.70
       2300.00          6.40
       2400.00          5.90]
[minValue, rowsToDelete1] = min(D(:,2))
[maxValue, rowsToDelete2] = max(D(:,2))
D([rowsToDelete1, rowsToDelete2], :) = [];  % Get rid of min(s) and max(es).
D % Print out

Best Answer

Related Solutions

MATLAB: Build 2-D array with same 1-D array

MATLAB: Removing maxium and minimum from the matrix

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