I have a structure myS with several fields, including myField, which in turns includes several other fields such as BB. I need to count how many time *'R_value' appears in BB.
I have tried:
sum(myS.myField.BB = 'R_value')
and this:
count = 0;
for i = 1:numel(myS.myField)
number_of_element = numel(myS.myField(i).BB)=='R_value'
count = count+number_of_element;
end
but it doesn't work. Any suggestion?
If you are just checking if BB is that literal string, then your loop is just:
count = 0;
for i = 1:numel(myS.myField)
count = count+strcmp(myS.myField(i).BB,'R_value')
end
numel counts how many elements are. Zero is an element. so is False. Just sum the array.
count = 0;
for i = 1:numel(myS.myField)
number_of_element = sum(myS.myField(i).BB==R_value)
count = count+number_of_element;
end
Also note you had the parenthesis wrong, so you where counting how many BB where in total, then comparing that number to R_value. I am assuming R_value is a number.
e.g.:
myS.myField(1).BB=[1 2 3 4 1 1 1]
myS.myField(2).BB=[4 5 65 1]
R_value=1
Related
My mat file contains 40,000 rows and two columns. I have to read it line by line
and then get values of last column in a single row.
Following is my code:
for v = 1:40000
firstRowB = data.d(v,:)
if(firstRowB(1,2)==1)
count1=count1+1;
end
if(firstRowB(1,2)==2)
count2=count2+1;
end
end
FirstRowB gets the row checks whether last column equals 1 or 2 and then increases the value of respective count by 1.
But I keep getting this error:
Reference to non-existent field 'd'.
You could use vectorization (it is always convenient especially in Matlab). Taking advantage of the fact that true is one and false is zero, if you just want to count you can do :
count1 = sum ( data.d(:, 2) == 1 ) ;
count2 = sum (data.d(:,2) == 2 ) ;
in fact in general you could define :
getNumberOfElementsInLastColEqualTo = #(numb) sum (data.d(:,end) == numb ) ;
counts =arrayfun( getNumberOfElementsInLastColEqualTo , [1 2 ] );
Hope this helps.
I have two datasets stored in a cell array and a double array, respectively. The design of the two arrays is:
Array 1 (name: res) (double) is composed of two columns; a unique id column and a data column.
Array 2 (name: config) (cell array) contains 3 column cells, each with a string inside. The last cell in the array contains a id double integer matching the id's in Array 1. The double integer in the cell array is converted to a double when necessary.
I want to merge the two datasets in order to have the 3 cells in the cell array AND the result column in Array 1 in one common cell array. How do I do this?
I have the following code. The code does not return the correct order of the results.
function resMat = buildResultMatrix(res, config)
resMat = {};
count = 1;
count_max = size(res,1)/130;
for i = 1 : size(res,1)
for j = 1 : size(res,1)
if isequal(res(i),str2double(config{j,3}))
if i == 1
resMat(end+1,:) = {config{j,:} res(j,2:end)};
else
if count == 1
resMat(end+1,:) = {config{j,:} res(j,2:end)};
elseif count == count_max
resMat(end+1,:) = {config{j,:} res(j,2:end)};
else
resMat(end+1,:) = {config{j,:} res(j,2:end)};
end
count = count + 1;
end
end
end
count = 1;
end
end
First convert the id in config to numbers:
config(:,3) = num2cell(str2double(config(:,3)));
Then run this:
res = sortrows(res,1);
config(:,4) = num2cell(res(cell2mat(config(:,3)),2))
this will put the data from res in the 4th column in config in the row with the same id.
I have the array "A" with values:
101 101
0 0
61.6320000000000 0.725754779522671
73.7000000000000 0.830301150185882
78.2800000000000 0.490917508345341
81.2640000000000 0.602561200211232
82.6880000000000 0.435568593909153
And I wish to remove this first row and retain the shape of the array (2 columns), thus creating the array
0 0
61.6320000000000 0.725754779522671
73.7000000000000 0.830301150185882
78.2800000000000 0.490917508345341
81.2640000000000 0.602561200211232
82.6880000000000 0.435568593909153
I have used A = A(A~=101); , which removes the values as required - however it packs the array down to one column.
The best way is:
A = A(2:end, :)
But you can also do
A(1,:) = []
however it is slightly less efficient (see Deleting matrix elements by = [] vs reassigning matrix)
If you are looking to delete rows that equal a certain number try
A = A(A(:,1)~=101,:)
Use all or any if you want to delete row if either all or any column equals your value:
A = A(all(A~=101,2),:)
I have a struct, that's a <1x1 struct>, and I'm trying to edit a field in the struct based on the values. The field is called GeoDist_Actual and the struct is called GeoDist_str. The field GeoDist_Actual is a <262792x1 double>, and this is the code I was trying to use in order to get rid of the values that are greater than 1.609344e+05.
i =1;
for i=i:size(GeoDist_str.GeoDist_Actual)
if GeoDist_str.GeoDist_Actual(i,1 > 1.609344e+05
GeoDist_str.GeoDist_Acutal(i,1) = [];
end
end
How would I append or alter this code in order to make it function like I'm aiming? I considered setting all the values to 0, but I'm going to have to go backwards from this in order to get back GPS values, doing a reverse-Vincenty(spherical) calculation, and I'd like to just completely get rid of the values that don't comply with the if condition.
If I can narrow down the question at all, let me know, and thank you for your help in advance!
Edit: I've noticed that when I changed out the section
GeoDist_str.GeoDist_Actual(i,1) = [];
for
GeoDist_str.GeoDist_Actual(i,1) = 0;
It didn't actually solve anything, instead it didn't access the field "GeoDist_Actual" within the struct "GeoDist_str", it just created a mirror field with values of 0.
Consider this example:
% a 10-by-1 vector
x = [1;2;3;4;5;6;7;8;9;10];
% remove entries where the value is less than five
x(x<5) = [];
This is called logical indexing, no need for loops.
Consider the following simple example:
A.a = 1:5;
A =
a: [1 2 3 4 5]
now delete all elements bigger 3;
A.a = A.a( ~(A.a > 3) );
A =
a: [1 2 3]
or alternatively:
A.a( A.a > 3 ) = []
For your case it's a little more bulky:
GeoDist_str.GeoDist_Actual = ...
GeoDist_str.GeoDist_Actual( ...
~(GeoDist_str.GeoDist_Actual > 1.609344e+05) )
So, presume a matrix like so:
20 2
20 2
30 2
30 1
40 1
40 1
I want to count the number of times 1 occurs for each unique value of column 1. I could do this the long way by [sum(x(1:2,2)==1)] for each value, but I think this would be the perfect use for the UNIQUE function. How could I fix it so that I could get an output like this:
20 0
30 1
40 2
Sorry if the solution seems obvious, my grasp of loops is very poor.
Indeed unique is a good option:
u=unique(x(:,1))
res=arrayfun(#(y)length(x(x(:,1)==y & x(:,2)==1)),u)
Taking apart that last line:
arrayfun(fun,array) applies fun to each element in the array, and puts it in a new array, which it returns.
This function is the function #(y)length(x(x(:,1)==y & x(:,2)==1)) which finds the length of the portion of x where the condition x(:,1)==y & x(:,2)==1) holds (called logical indexing). So for each of the unique elements, it finds the row in X where the first is the unique element, and the second is one.
Try this (as specified in this answer):
>>> [c,~,d] = unique(a(a(:,2)==1))
c =
30
40
d =
1
3
>>> counts = accumarray(d(:),1,[],#sum)
counts =
1
2
>>> res = [c,counts]
Consider you have an array of various integers in 'array'
the tabulate function will sort the unique values and count the occurances.
table = tabulate(array)
look for your unique counts in col 2 of table.