My picture has a certain number of various shapes of blobs. I want to store those centroid values in one array for the future use. So I tried the following code, but it did not work. So can anyone help me?
Sample:
for i = 1:length(STATS)
centroid = STATS(i).Centroid;
array = zeros(length(STATS));
array(i) = centroid;
end
I want to store the centroid data in one array like below
array=
145 145
14 235
145 544
14 69
74 55
Try the following:
for i = 1:length(STATS)
array{i} = STATS(i).Centroid;
end
You can print the entire array using the following:
array{:}
You can read more about cell arrays here. Also, in your older code, you were trying to assign an array (Centroid) to an element of an array(array(i)).
How about:
array=cell2mat({STATS.Centroid});
Assuming
STATS(1).Centroid = [145 145];
STATS(2).Centroid = [14 235]; % Etc...
Try:
array = reshape([STATS.Centroid],2,size(STATS,2))'
array =
145 145
14 235
145 544
14 69
74 55
How this works:
[STATS.Centroid] is a short version of [STATS(1).Centroid, STATS(2).Centroid, .. STATS(n).Centroid]. This will give you the values as a vector. reshape is then used to make it into your desired size.
Related
Consider that I have a code that returns a double array. When run, the result returned at the command window a result looks like this:
mpc.gen=
1 100 344 34 5
2 433 223 45 2
3 333 432 12 3
4 213 233 12 3
What I want to do is create a MATLAB script which would contain this array. In other words in this new MATLAB script I would have the following array, constructed like this:
mpc.gen= [ 1 100 344 34 5 ;
2 433 223 45 2 ;
3 333 432 12 3 ;
4 213 233 12 3 ;
] ;
Just calling the function would save the variable in the new script, however that is not what I need since I need to use this script for a simulation at a special power tool called MATPOWER. The array needs to be in the form shown at the new script.
The actual array is much bigger in size however I use this here for simplicity. Is there any way I can do this automatically, and not just pass the data from the command window to the new script one by one manually? Any help would be greatly appreciated. Thank you in advance for your time!
What you want to use is mat2str. It converts a matrix to a string representation that, when evaluated, results in the identical matrix.
For example:
>> result = [1 100 344 34 5;
2 433 223 45 2;
3 333 432 12 3;
4 213 233 12 3];
>> mat2str(result)
ans =
[1 100 344 34 5;2 433 223 45 2;3 333 432 12 3;4 213 233 12 3]
You could write this to a file like so:
f = fopen('test_script.m', 'w');
fprintf(f,'mpc.gen = %s\n', mat2str(result));
fclose(f);
The formatting is not identical to your example, but if the tool does proper MATLAB parsing, it shouldn't be a problem.
Is it intentional that mpc is a struct? (you are using dot in the name.) In the following, I use underscore instead, but it can certainly be adopted, if it is intentional.
This is what functions are for. So instead of making a script, you should create a new function. If I were to do what you want to do, I would have 2 functions and 1 script. Whereas the script looks like this
mpc_bus = function1;
function2(mpc_bus);
where function1 is the code that returns mpc.bus and function2 is the one where you want to work with mpc.gen, and the top would be something like this
function [] = function2(mpc_gen)
Alternatively: If you of some reason does not like functions, you can make the first code save the variable using save(*filename*.mat) and then you can load the file again in the script using dat=load(*filename*.mat); and mpc_gen = dat.mpc_bus;
I have a bunch of .txt text files. this file is included like this
e.g.
text1.txt-
1
44
22
100
..
..
text2.txt-
7
14
82
50
..
..
....
text260.txt-
31
4
62
700
..
..
like this, text#.txt have almost 260 files.
I want to load into MATLAB with array like this.
a =
1 7 ... 31
44 14 ... 4
22 82 ... 62
100 50 ... 700
.. .. ... ..
.. .. ... ..
As I know, the load() function is in MATLAB. But I don't know how to load into array format.
How to load the multiple data to x by x array in MATLAB ?
You would have to slowly build up the array. My first thought would be to do this:
arr = [];
for i = 1:260
arr = [arr; load(['text' num2str(i) '.txt'])'];
end
You start off with an empty array, and then iterate through the files, appending each file to the array. NB, if the final array is quite large you might want to consider a different approach involving pre-allocating the array:
arr = zeros(length(load('text1.txt')), 260);
for i = 1:260
arr(:,i) = load(['text' num2str(i) '.txt'])';
end
I have an array in MATLAB
For example
a = 1:100;
I want to select the first 4 element in every successive 10 elements.
In this example I want to b will be
b = [1,2,3,4,11,12,13,14, ...]
can I do it without for loop?
I read in the internet that i can select the element for each step:
b = a(1:10:end);
but this is not working for me.
Can you help me?
With reshape
%// reshaping your matrix to nx10 so that it has successive 10 elements in each row
temp = reshape(a,10,[]).'; %//'
%// taking first 4 columns and reshaping them back to a row vector
b = reshape(temp(:,1:4).',1,[]); %//'
Sample Run for smaller size (although this works for your actual dimensions)
a = 1:20;
>> b
b =
1 2 3 4 11 12 13 14
To vectorize the operation you must generate the indices you wish to extract:
a = 1:100;
b = a(reshape(bsxfun(#plus,(1:4)',0:10:length(a)-1),[],1));
Let's break down how this works. First, the bsxfun function. This performs a function, here it is addition (#plus) on each element of a vector. Since you want elements 1:4 we make this one dimension and the other dimension increases by tens. this will lead a Nx4 matrix where N is the number of groups of 4 we wish to extract.
The reshape function simply vectorizes this matrix so that we can use it to index the vector a. To better understand this line, try taking a look at the output of each function.
Sample Output:
>> b = a(reshape(bsxfun(#plus,(1:4)',0:10:length(a)-1),[],1))
b =
Columns 1 through 19
1 2 3 4 11 12 13 14 21 22 23 24 31 32 33 34 41 42 43
Columns 20 through 38
44 51 52 53 54 61 62 63 64 71 72 73 74 81 82 83 84 91 92
Columns 39 through 40
93 94
I would like to create an array or vector of musical notes using a for loop. Every musical note, A, A#, B, C...etc is a 2^(1/12) ratio of the previous/next. E.G the note A is 440Hz, and A# is 440 * 2^(1/12) Hz = 446.16Hz.
Starting from 27.5Hz (A0), I want a loop that iterates 88 times to create an array of each notes frequency up to 4186Hz, so that will look like
f= [27.5 29.14 30.87 ... 4186.01]
So far, I've understood this much:
f = [];
for i=1:87,
%what goes here
% f = [27.5 * 2^(i/12)]; ?
end
return;
There is no need to do a loop for this in matlab, you can simply do:
f = 27.5 * 2.^((0:87)/12)
The answer:
f =
Columns 1 through 13
27.5 29.135 30.868 32.703 34.648 36.708 38.891 41.203 43.654 46.249 48.999 51.913 55
Columns 14 through 26
58.27 61.735 65.406 69.296 73.416 77.782 82.407 87.307 92.499 97.999 103.83 110 116.54
Columns 27 through 39
123.47 130.81 138.59 146.83 155.56 164.81 174.61 185 196 207.65 220 233.08 246.94
Columns 40 through 52
261.63 277.18 293.66 311.13 329.63 349.23 369.99 392 415.3 440 466.16 493.88 523.25
Columns 53 through 65
554.37 587.33 622.25 659.26 698.46 739.99 783.99 830.61 880 932.33 987.77 1046.5 1108.7
Columns 66 through 78
1174.7 1244.5 1318.5 1396.9 1480 1568 1661.2 1760 1864.7 1975.5 2093 2217.5 2349.3
Columns 79 through 88
2489 2637 2793.8 2960 3136 3322.4 3520 3729.3 3951.1 4186
maxind = 87;
f = zeros(1, maxind); % preallocate, better performance and avoids mlint warnings
for ii=1:maxind
f(ii) = 27.5 * 2^(ii/12);
end
The reason I named the loop variable ii is because i is the name of a builtin function. So it's considered bad practice to use that as a variable name.
Also, in your description you said you want to iterate 88 times, but the above loop only iterates 1 through 87 (both inclusive). If you want to iterate 88 times change maxind to 88.
I have a 1x280 structure in Matlab. In order for me to use the values, I changed it to struct2cell array.
An example of how one of the structures among the 280 looks is below :
Field Value Min Max
point1 [29,469] 29 469
point2 [42,469] 42 469
-------------------------------------------
After changing to a cell array using the below code:
showlines = struct(lines);
cellData = struct2cell(showlines);
cellData{1,1}(1)
= 29
However, if I use this :
cellData{1,1:280}(1);
There is an error
Error:: bad cell reference operation
I would need to keep all the x values of point1 in each of the 280 structures into an array so as to find out the maximum X value of point1 in them. Any idea how to do it?
Thank you very much in advance.
Although not a direct answer to your question, you might be interested to know that
%# some example data
S(1).point1 = [29 469];
S(1).point2 = [42 469];
S(2).point1 = [30 470];
S(2).point2 = [43 470];
...
S(280).point1 = [130 870];
S(280).point2 = [243 970];
%# transform to regular array
pt1 = reshape([S.point1],[],2).';
pt2 = reshape([S.point2],[],2).';
will result in
pt1 = [29 469 pt2 = [42 469
30 470 43 470
... ...
130 870]; 243 970];
which enables you to do things like
>> pt1(:, 2)
ans =
469
470
..
870
>> min(pt1(:,1))
ans =
29
Does that solve your problem?
To any passers by: what is the notation [S.field] for non-scalar structs called? Does it even have a name? Questions involving this technique frequently pop-up, and it would help if I knew what it's called so I can post a link to the manual page in the answer...