I want to create array of MSERRegions class.Basically i have one array of same type returned by function detectMSERFeatures.See code snippet below
regions = detectMSERFeatures(gray_input)
%gray_input is any image in gray scall form
for (i =2:length(regions))
if(length(regions(i).PixelList)>100)
% Here i want to copy all such regions in new object array say of name regions_new
j=j+1;
end
end
How can this be done?
You cannot have an array of MSERRegions objects. You should use a cell array instead.
You can declare an MSER Array in MatLab like this:
regions = MSERRegions();
And add them into the array like this:
regions(1,1) = mserRegions(i,1);
So:
regions_new = MSERRegions();
j = 1;
for (i = 1:length(regions))
if(length(regions(i).PixelList)>100)
regions_new(j,1) = regions(i,1)
j = j + 1;
end
end
Related
Suppose a MATLAB program is written as:
c=5;
a=4.5;
m=14;
for i=1:14
a=c*a;
end
How do I store the values of a? I wish to use the values of a later.
You need to store previous values of a in an array. You can pre-allocate the array outside of your loop and then fill it each time through your loop.
a = zeros(1, 15);
a(1) = 4.5;
for k = 1:14
a(k + 1) = c * a(k);
end
last_a = a(end);
A short form of #Suever's answer, can be written like that:
c=5;
a=4.5*c.^(0:14);
The results are:
a=
4.50000000000000 22.5000000000000 112.500000000000 562.500000000000 2812.50000000000 14062.5000000000 70312.5000000000 .......
I want to store efficiently some numbers as strings (with different lengths) into a table. This is my code:
% Table with numbers
n = 5;
m = 5;
T_numb = array2table((rand(n,m)));
% I create a table with empty cells (to store strings)
T_string = array2table(cell(n,m));
for i = 1:height(T_numb)
for ii = 1:width(T_numb)
T_string{i,ii} = cellstr(num2str(T_numb{i,ii}, '%.2f'));
end
end
What could I do to improve it? Thank you.
I don't have access to the function cell2table right now, but using the undocumented function sprintfc might work well here (check here for details).
For instance:
%// 2D array
a = magic(5)
b = sprintfc('%0.2f',a)
generates a cell array like this:
b =
'17.00' '24.00' '1.00' '8.00' '15.00'
'23.00' '5.00' '7.00' '14.00' '16.00'
'4.00' '6.00' '13.00' '20.00' '22.00'
'10.00' '12.00' '19.00' '21.00' '3.00'
'11.00' '18.00' '25.00' '2.00' '9.00'
which you can convert to a table using cell2table.
So in 1 line:
YourTable = cell2table(sprintfc('%0.2f',a))
This seems to be quite fast -
T_string = cell2table(reshape(strtrim(cellstr(num2str(A(:),'%.2f'))),size(A)))
Or with regexprep to replace strtrim -
cell2table(reshape(regexprep(cellstr(num2str(A(:),'%.2f')),'\s*',''),size(A)))
Here, A is the 2D input numeric array.
I'm trying to create a function that reads in a field of a structure to create a vector of fields. I have a structure of the form:
subject(i).stride(j).strideLength
and there are 10 subjects, about 10 strides per subject. I can create a long vector of the strideLength of all subjects, all strides with code like this:
k = 1;
for i=1:10
for j=1:size(subject(i).stride, 2)
varVector(k) = subject(i).stride(j).strideLength;
k = k + 1;
end
end
however, there are a lot of different fields I want to do this with, and I'd like to do it with a function that I can call like this:
x(1) = groupData(strideLength);
but I can't figure out the syntax to append strideLength to subject(i).stride(j). within the above loop in a function. This is what I hoped would work and didn't:
function [varVector] = groupData(var)
%groupData returns a concatenated vector of a given variable (speed, etc.)
k = 1;
for i=1:10
for j=1:size(subject(i).stride, 2)
varVector(k) = subject(i).stride(j).var;
k = k + 1;
end
end
end
Any thoughts on how to do this right? Thanks in advance!
In your groupData function, pass in the field/variable name as a string
x(1) = groupData('strideLength');
Then in the body of the code, access this field as follows
varVector(k) = subject(i).stride(j).(var);
Try the above and see what happens!
I am loading a file ...
obj = load('foo1.txt');
% obj is a double array of size (NY,NX)
However, there are many such files and I wish to parse then save them in an array
asdf = zeros(1, numObjs);
for index = 1:numObjs
obj = load(sprintf(foo%d.txt,index));
asdf(index) = obj;
end
In this case, the procedure fails since the number of objects in asdf(i), namely the size of i ... which is one ~= the size of obj ... sizeof(obj).
I tried fooling around with a struct, but couldn't find a suitable solution.
Thanks.
You can use a cell array instead:
asdf{numObjs} = []; % intialises; does not preallocate memory for cell contents
for index = 1:numObjs
asdf{index} = load(sprintf(foo%d.txt,index));
end
I have hit a roadblock where I am trying to iterate through a structure formed in the MATLAB workspace inside an EML (Embedded Matlab) function block in SIMULINK. Here is some example code:
% Matlab code to create workspace structure variables
% Create the Elements
MyElements = struct;
MyElements.Element1 = struct;
MyElements.Element1.var1 = 1;
MyElements.Element1.type = 1;
MyElements.Element2 = struct;
MyElements.Element2.var2 = 2;
MyElements.Element2.type = 2;
MyElements.Element3 = struct;
MyElements.Element3.var3 = 3;
MyElements.Element3.type = 3;
% Get the number of root Elements
numElements = length(fieldnames(MyElements));
MyElements is a Bus type Parameter for the MATLAB Function Block (EML) in SIMULINK. Below is the area I am running into trouble with. I know the number of elements inside my struct and I know the names, but the number of elements can change with any configuration. So I cannot hardcode based on the Element names. I have to iterate through the struct inside the EML block.
function output = fcn(MyElements, numElements)
%#codegen
persistent p_Elements;
% Assign the variable and make persistent on first run
if isempty(p_Elements)
p_Elements = MyElements;
end
% Prepare the output to hold the vars found for the number of Elements that exist
output= zeros(numElements,1);
% Go through each Element and get its data
for i=1:numElements
element = p_Elements.['Element' num2str(i)]; % This doesn't work in SIMULINK
if (element.type == 1)
output(i) = element.var1;
else if (element.type == 2)
output(i) = element.var2;
else if (element.type == 3)
output(i) = element.var3;
else
output(i) = -1;
end
end
Any thoughts on how I can iterate through a struct type in SIMULINK? Also, I cannot use any extrinsic functions like num2str because this is to be compiled on a target system.
I believe you are trying to use dynamic field names for structures. The correct syntax should be:
element = p_Elements.( sprintf('Element%d',i) );
type = element.type;
%# ...