MATLAB: Calculate the average for each column

I have a matrix called d=

[99  99  0.100  0.120  0  0.500  0;
0       0  0       0       0.150   0.120   0;
0.110  0.010  0.010  0  0  0.300  0.100;
0  0.250  0  0.050  0.060  0.100  0.110;
0  0.120  0.040  0  0.500  0.750  99];

I want to calculate the average of each column but since I have to take the 99's out. the 99's are located at the first row and last row of the matrix

so far I have

for i=1:5;
weekly_a=mean(d(d(:,i)<99)

since I took the 99 for the first column matlab has as the answ=0.0275 when the correct answer should be 0.022

any sugestion about this?

Best Answer

mean( d( d(:,i)<99, i) )

Notice you had the "i" second dimension missing.

Related Solutions

MATLAB: How to extract specific rows from one array to another array

The problem is that you test for equivalence of floating point values. This is bound to cause errors, as has been discussed hundreds of times on this forum:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

https://www.mathworks.com/matlabcentral/answers/350303-why-0-6-is-not-equal-to-0-2-3

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

etc., etc.

The solution is to use ismembertol, or compare the absolute difference against some tolerance value:

idx = false(size(NA2,1),1);
tol = 0.0001;
for k = 1:size(CapacityOut,1)
   idx = idx | abs(NA2(:,1)-CapacityOut(k))<tol;
end
out = NA2(idx,:);

giving:

>> out
out =
   0.00000   0.98000   1.00000   0.02000  -3.10000   1.00000   1.00000
   1.10000   0.98000   0.05910   0.02000  -2.00000   1.00000   0.07790
   2.00000   0.98000   0.03000   0.02000  -1.10000   1.00000   0.04940
   3.10000   0.98000   0.00000   0.02000  -0.00000   1.00000   0.02000
   4.20000   0.98000   0.00000   0.02000   1.10000   0.05910   0.00120
   5.10000   0.98000   0.00000   0.02000   2.00000   0.00000   0.00000
   6.20000   0.98000   0.00000   0.02000   3.10000   0.00000   0.00000
>>

MATLAB: Longest wet and dry spell of the matrix

Once again, this is a situation that would be trivial if you had the Image Processing Toolbox because in one line of code you can find the lengths of all non-zero stretches of rainfall for a column. One more line of code would tell you the longest of those stretches. Do you have that toolbox? Type ver to find out. If you do, try this code:

a=[99  99  0.100  0.120  0  0.500  0;
0       0  0       0       0.150   0.120   0;
0.110  0.010  0.010  0  0  0.300  0.100;
0  0.250  0  0.050  0.060  0.100  0.110;
0  0.120  0.040  0  0.500  0.750  99]
[rows columns] = size(a);
for row = 1 : rows
  measurements = regionprops(a(row, :)< 99 & a(row, :) > 0, 'Area');
  % Get all the stretches of rain
  allRains = [measurements.Area]
  % Get the longest rain.
  longestStretch = max(allRains);
  fprintf('For row %d, the longest stretch with rain = %d.\n\n', ...
    row, longestStretch);
end

In the command window:

allRains =
     2     1
For row 1, the longest stretch with rain = 2.
allRains =
     2
For row 2, the longest stretch with rain = 2.
allRains =
     3     2
For row 3, the longest stretch with rain = 3.
allRains =
     1     4
For row 4, the longest stretch with rain = 4.
allRains =
     2     2
For row 5, the longest stretch with rain = 2.

Best Answer

Related Solutions

MATLAB: How to extract specific rows from one array to another array

MATLAB: Longest wet and dry spell of the matrix

Related Question