Get the Array Number, when value changes
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Hello, I have the following array:
1 Monday
2 Monday
3 Monday
4 Sunday
5 Sunday
6 Friday
7 Friday
8 Friday
...
I would like to get the array number when the value changes. These are the "limits" for the values. Then I want to save these limits in new arrays, in this case:
Limits.Monday:
1
3
Limits.Sunday:
4
5
Limits.Friday
6
8
Thanks :-)
回答（5 个）
Andrei Bobrov
2015-7-29
编辑：Andrei Bobrov
2015-7-29
A = {1 'Monday'
2 'Monday'
3 'Monday'
4 'Sunday'
5 'Sunday'
6 'Friday'
7 'Friday'
8 'Friday'};
[a,~,c] = unique(A(:,2),'stable');
Limits = cell2struct(accumarray(c,cell2mat(A(:,1)),[],@(x){[min(x);max(x)]}),a,1);
add variant
A = {1 'Monday'
2 'Monday'
3 'Monday'
4 'Sunday'
5 'Sunday'
6 'Monday'
7 'Monday'
8 'Friday'};
[a,~,c] = unique(A(:,2),'stable');
i1 = [true;diff(c)~=0];
x = accumarray(cumsum(i1),cell2mat(A(:,1)),[],@(x){[min(x);max(x)]});
y = strcat(A(i1,2),{'_'},arrayfun(@(x)sprintf('%d',x),(1:nnz(i1))','un',0));
Limits = cell2struct(x,y,1);
Try this:
X = {1,'Monday';2,'Monday';3,'Monday';4,'Sunday';5,'Sunday';6,'Monday';7,'Monday'};
Y = [true;any(diff(char(X(:,2)),1,1),2);true];
idx = cumsum(Y(1:end-1));
out(:,2) = accumarray(idx,[X{:,1}],[],@(x){x([1,end])});
out(:,1) = X(Y(1:end-1),2);
and here is the output in the command window:
>> out
out =
'Monday' [2x1 double]
'Sunday' [2x1 double]
'Monday' [2x1 double]
>> out{1,2}
ans =
1
3
>> out{2,2}
ans =
4
5
>> out{3,2}
ans =
6
7
I did not put the data into a structure because while a structure with fields Monday, Tuesday, etc, makes perfect sense, placing indices in front of the names a) is not a valid variable/fieldname in MATLAB, and b) implies that the sequence order is significant, therefore an indexed container (e.g. a cell array) is more suitable.
Marv
2015-10-4
0 个投票
1 个评论
The data matrix that you uploaded does not match the question. Your question states "I have the following array:"
1 Monday
2 Monday
3 Monday
4 Sunday
...
but your data file consists of a single vector of type double containing decimal values. This is a completely different format to what you question is asking about. If you want help then you need to provide clear explanations for us, and make sure that your data makes sense.
Do you want us the use your uploaded data, which has nothing to do with your question, or shall we invent some data ourselves?
You should read this, and please put into practice what it advises:
Given your uploaded data (attached below), this code will identify the locations where the value changes:
tol = 0.01;
data = load('Log_data_Changing_Value.mat');
idx = find(diff(data.A)>tol)
and it displays these in the command window:
idx =
57
585
1535
1997
2438
4298
If you explain exactly what you need to do with these indices then we can help you to use them too.
4 个评论
Marv
2015-10-5
Where does the 6.1 come from? It is not the value in the array at those locations.
>> data.A(idx)
ans =
0.00000
0.00000
11.00528
12.10609
0.00000
7.00354
In fact none of the rows close to those indices have those values:
>> data.A(1530:1540)
ans =
11.005
11.005
11.005
11.005
11.005
11.005
13.006
13.006
13.006
13.006
13.006
>> data.A(1990:2000)
ans =
12.106
12.106
12.106
12.106
12.106
12.106
12.106
12.106
12.306
12.306
12.306
Marv
2015-10-5
Correct. This is called indexing, and is a basic tool used in MATLAB for accessing data. To learn how to use indexing your should work through some of the tutorials:
And if my Answer has helped you please click on Accept.
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