Comparing elements of a vector.

I have two vectors named R and T, where elements in R keep on increasing and finally reaches a steady state value.

Let's say T = [1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21] and R = [1;2;3;4;5;6;7;8;9;10;10;10;11;12;12;12;12;12;13;13;13].

I intend to get g(:,1) = [1;2;3;4;5;6;7;8;9;10;13;14;19] and g(:,2) = [1;2;3;4;5;6;7;8;9;10;11;12;13]. But I am getting all the values in g. Could you please help me out with this.

Thanks and Regards.

L = length(R);
for h = 1:1:L-1
    dffrad = R(h+1)-R(h);
    dfftime= T(h+1)-T(h);
    if (dffrad~=0 && dffrad>0)
        g = [g; T(h+1) R(h+1)];
    end
end

[Shubham Gupta]

I am getting the output that you needed, using the code that you have provided. I don't see any problem.

T = [1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17;18;19;20;21];
R = [1;2;3;4;5;6;7;8;9;10;10;10;11;12;12;12;12;12;13;13;13];
g = [1,1];
L = length(R);
for h = 1:1:L-1
    dffrad = R(h+1)-R(h);
    dfftime= T(h+1)-T(h);
    if (dffrad~=0 && dffrad>0)
        g = [g; T(h+1) R(h+1)];
    end
end

Output is

g =

     1     1
     2     2
     3     3
     4     4
     5     5
     6     6
     7     7
     8     8
     9     9
    10    10
    13    11
    14    12
    19    13

Am I misunderstanding something?

[Madhurima Reddy]

The values in my data(not that's given in the question) were getting rounded off to nearest decimal and that's why I thought the values were repeating. Thank you Shubham for your help.

[Shubham Gupta]

I am glad I could help. Also, you might wanna look at @the_cyclist 's answer for better performance.

Answer 1

[the cyclist]

[g(:,2), idx] = unique(R);
g(:,1) = T(idx);

[Shubham Gupta]

There is one problem with that, when data decreases at some point user don't want to take that point but unique will take that data into the account. For e.g.

R = [1,2,3,4,5,7,6,8,10,10,10,11,11,11];
T = [1,2,3,4,5,6,7,8,9,10,11,12,13,14];
[g(:,2), idx] = unique(R);
g(:,1) = T(idx);

will output

g =

     1     1
     2     2
     3     3
     4     4
     5     5
     7     6  % user wouldn't want this data
     6     7
     8     8
     9    10
    12    11

That being said, if data is monotically increasing or there is always unit difference between current and successive value then it should be no problem at all.

[the cyclist]

You are correct.

But the original question explicitly stated that R is increasing, so I assumed that that was OK.

[Madhurima Reddy]

My data does decrease after reaching a max value. However, Thank you to both of you for help.