Get the Array Number, when value changes

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 :-)

[Marv]

I forgot to mention that there could be several values with the same name, for example:

1  Monday
2  Monday
3  Monday
4  Sunday
5  Sunday
6  Monday
7  Monday
...

Is it possible to get all limits by increasing order ?

Limits.1_Monday
1
3

Limits.2_Sunday
4
5

Limits.3_Monday
6
7

Answer 1

[Andrei Bobrov]

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);

[Marv]

I think this solutions outputs the number in the left column ? But I would like to output the array number, like:

Range_Monday=A(1:3,2) 
= A(Limits.1_Monday(1,1),Limits.1_Monday(2,1))

[Andrei Bobrov]

See 'add variant' from my answer.

Answer 2

[Stephen23]

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.

Answer 3

[Marv]

Hm I still dont have the right solution.

Attached I uploaded you the data I want to analyse.

Every time the value changes, I want to get the array / column number where it changed. The output shall be a range, same as in the example above.

The problem is that there are several values with different ranges, for example: '0' is from column 1 to 57 but also from 5016 to 5110 !

So can you output the ranges chronologically please ? Like 'Range'_ChronologicNr_ArrayValue:

Range_1_0 = 

      [1]
      [57]

Range_2_6.1029 = 

      [58]
      [529]

Range_3_0 = 

      [530]
      [585]

Range_4_13.0064 = 

      [586]
      [852]

Range_5_11.0053 = 

      [853]
      [1535]

Thanks :)

[Thorsten]

You forgot to attach the file.

[Marv]

Sorry, above is the attached file.

Answer 4

[Marv]

Can someone help me ? I need a solution today :-/

[Stephen23]

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:

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 5

[Stephen23]

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.

[Marv]

Works, but I also need to know the value for each limit (array number), like this:

ans =
        57 -> 0
       585 -> 0
      1535 -> 6.1
      1997 -> 6.1
      2438
      4298

[Stephen23]

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]

Alright, so I need "data.A(idx)" to export the values ?

[Stephen23]

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:

http://www.mathworks.com/help/matlab/getting-started-with-matlab.html

And if my Answer has helped you please click on Accept.