How to select particular rows from a large matrix ?

I have been working with the satellite data. So I have exported some data into matlab which contains nearly 16,000 rows and 6 columns. The first 2 columns are latitude and longitude and next columns contain various data fields like CO2 etc. what should I do to select the data that lies between particular latitude and longitudes. like limits of latitude are 20 to 30 and limits of longitude are 40 to 50.

Answer 1

[kjetil87]

small example: x=zeros(6,6); x(:)=1:numel(x)

x =

     1     7    13    19    25    31
     2     8    14    20    26    32
     3     9    15    21    27    33
     4    10    16    22    28    34
     5    11    17    23    29    35
     6    12    18    24    30    36

% now select the row(s) that have first column number between 3 and 5

    x(x(:,1)>2 & x(:,1)<6 , :)

% if you want to add constraints on column 2 aswell:

x( x(:,1)>2 & x(:,1)<6 & x(:,2)>8 & x(:,2)<11 , :)

[srinivasarao tanniru]

thankyou

[Vasilis Mitropoulos]

thanks and cheers!!

Answer 2

[suresh s]

yes, we can do in Matlab

Example:

>> a=magic(4)

a =

    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1

>> a(2:4,2:4)

ans =

    11    10     8
     7     6    12
    14    15     1

ans is row from 2 to 4 and column from 2 to 4

NOTE: In matlab Matrix always start from 1

Answer 3

[Milan Vasiç]

I want to form a table like this:

I wrote the code:

u = 8;
z1 = 13;
FI_K0 = 45;

for b = 0:10:180
    fprintf('%5d', b)
    
    for j=1:u
       FI_K (j) = FI_K0 + (j - 1) * (360. / u) - (b / z1)
        
    end
        
end

In Command Window I get the following results:

0

FI_K = 45

FI_K = 45 90

FI_K = 45 90 135

FI_K = 45 90 135 180

FI_K = 45 90 135 180 225

FI_K = 45 90 135 180 225 270

FI_K = 45 90 135 180 225 270 315

FI_K = 45 90 135 180 225 270 315 360

10

FI_K = 44.2308 90.0000 135.0000 180.0000 225.0000 270.0000 315.0000 360.0000

FI_K = 44.2308 89.2308 135.0000 180.0000 225.0000 270.0000 315.0000 360.0000

FI_K = 44.2308 89.2308 134.2308 180.0000 225.0000 270.0000 315.0000 360.0000

FI_K = 44.2308 89.2308 134.2308 179.2308 225.0000 270.0000 315.0000 360.0000

FI_K = 44.2308 89.2308 134.2308 179.2308 224.2308 270.0000 315.0000 360.0000

FI_K = 44.2308 89.2308 134.2308 179.2308 224.2308 269.2308 315.0000 360.0000

FI_K = 44.2308 89.2308 134.2308 179.2308 224.2308 269.2308 314.2308 360.0000

FI_K = 44.2308 89.2308 134.2308 179.2308 224.2308 269.2308 314.2308 359.2308

20

FI_K = 43.4615 89.2308 134.2308 179.2308 224.2308 269.2308 314.2308 359.2308

FI_K = 43.4615 88.4615 134.2308 179.2308 224.2308 269.2308 314.2308 359.2308

FI_K = 43.4615 88.4615 133.4615 179.2308 224.2308 269.2308 314.2308 359.2308

FI_K = 43.4615 88.4615 133.4615 178.4615 224.2308 269.2308 314.2308 359.2308

FI_K = 43.4615 88.4615 133.4615 178.4615 223.4615 269.2308 314.2308 359.2308

FI_K = 43.4615 88.4615 133.4615 178.4615 223.4615 268.4615 314.2308 359.2308

FI_K = 43.4615 88.4615 133.4615 178.4615 223.4615 268.4615 313.4615 359.2308

FI_K = 43.4615 88.4615 133.4615 178.4615 223.4615 268.4615 313.4615 358.4615

I need the following result:

0

FI_K = 45 90 135 180 225 270 315 360

10

FI_K = 44.2308 89.2308 134.2308 179.2308 224.2308 269.2308 314.2308 359.2308

20

FI_K = 43.4615 88.4615 133.4615 178.4615 223.4615 268.4615 313.4615 358.4615

How do I do this?