How to detect a data value change in matlab

looking for yur help one more time.

I have data that is constanly hanging, here I share one portion of it

I'm trying to create a variable/falg that helps me to identify when there is a change, somethinng like this:

DATA variable/flag

0 -----> matlab code -----> 0

0 0

0 0

0.1224 1

0.1219 1

0.1199 1

0.1199 0

0.1199 0

0.1175 1

0.1175 0

0.1175 0

0.1175 0

0.1300 1

0.1300 0

0.1200 1

DATA values can change any time, keep same value for different periods of time, and either increase, decrease or change to positive or negative side.

I don't have much experience with mat lab so any feedback will be highly appreciated.

thanks

Answer 1

[Voss]

DATA = [
    0
    0
    0
    0.1224
    0.1219
    0.1199
    0.1199
    0.1199
    0.1175
    0.1175
    0.1175
    0.1175
    0.1300
    0.1300
    0.1200
    ];

is_change = [false; diff(DATA) ~= 0]

is_change = 15x1 logical array
   0
   0
   0
   1
   1
   1
   0
   0
   1
   0
   0
   0
   1
   0
   1

% a table for viewing is_change alongside DATA
result = table(DATA,is_change)

result = 15x2 table
     DATA     is_change
    ______    _________

         0      false  
         0      false  
         0      false  
    0.1224      true   
    0.1219      true   
    0.1199      true   
    0.1199      false  
    0.1199      false  
    0.1175      true   
    0.1175      false  
    0.1175      false  
    0.1175      false  
      0.13      true   
      0.13      false  
      0.12      true   

[A-Rod]

awsome, this works and it helps me a lot, thankyou for taking time to share.

[Voss]

You're welcome!

[A-Rod]

Voss.

I ran into a problem when my data goes negative, I need to make my flag true when data values are negative even if they don't change, like this:

DATA variable/flag

0 -----> matlab code -----> 0

0 0

0 0

0.1224 1

0.1219 1

0.1199 1

0.1199 0

0.1199 0

0.1175 1

0.1175 0

0.1175 0

0.1175 0

0.1300 1

0.1300 0

0.1200 1

-0.0007 1

-0.0007 1

-0.0007 1

-0.0082 1

-0.0081 1

0.1200 1

0.1200 0

];

I tried to complement the logical function you shared:

is_change = [false; diff(DATA) ~= 0 & true; DATA<0]

but is not working as I expected since the output is a vector 2 times the length of DATA.

is there a way to combine it and get just one vector with the length of DATA but keeping both logical conditions? like the column like the one shown in desired output

DATA is_change

output desired output

0 false false

0 false false

0 false false

0.1224 true true

0.1219 true true

0.1199 true true

0.1199 false false

0.1199 false false

0.1175 true false

0.1175 false false

0.1175 false false

0.1175 false false

0.13 true true

0.13 false false

0.12 true true

-0007 false true

-0007 false true

-0007 false true

-0082 false true

-0081 false true

0.12 true true

0.12 false true

false

false

false

false

false

false

false

false

false

false

false

false

false

false

false

true

true

true

true

true

false

false

I thank you in advance and I stay tuned for any update

[Voss]

DATA = [
    0
    0
    0
    0.1224
    0.1219
    0.1199
    0.1199
    0.1199
    0.1175
    0.1175
    0.1175
    0.1175
    0.1300
    0.1300
    0.1200
     -0007
     -0007 
     -0007 
     -0082 
     -0081 
    0.12   
    0.12    
    ];

is_change = [false; diff(DATA) ~= 0] | DATA<0

is_change = 22x1 logical array
   0
   0
   0
   1
   1
   1
   0
   0
   1
   0
   0
   0
   1
   0
   1
   1
   1
   1
   1
   1
   1
   0

% a table for viewing is_change alongside DATA
result = table(DATA,is_change);
disp(result)

     DATA     is_change
    ______    _________

         0      false  
         0      false  
         0      false  
    0.1224      true   
    0.1219      true   
    0.1199      true   
    0.1199      false  
    0.1199      false  
    0.1175      true   
    0.1175      false  
    0.1175      false  
    0.1175      false  
      0.13      true   
      0.13      false  
      0.12      true   
        -7      true   
        -7      true   
        -7      true   
       -82      true   
       -81      true   
      0.12      true   
      0.12      false  

[A-Rod]

thank you so much!

[Voss]

You're welcome!