Assign values in a matrix

My script considers charging of Electric Vehicles. The first column is when the EV starts charging (in what minute), the second how much is charged, the third how long it charges. Example

3849 1 4

I would like to add values so the matrix looks like this, the values in the third column is now not relevant as it is expressed in per minute

3849 0.25 1

3850 0.25 1

3851 0.25 1

3852 0.25 1

[Jorg Woehl]

Hi Joel, I am not quite clear on what you would like to do... Do you want to change all values in the second column of your n-by-3 matrix to 0.25? Or is this a conditional assignment, like in "if the second column is 1, then change it to 0.25"? And reset the third column to 1 at the same time? Or do you want to "add values", like you are saying, i.e. add new rows to your matrix where the value in the first column (charging start time) increases by 1 from one row to the next?

[Joel Schelander]

The car is charged 1 kWh at time 3849 for 4 minutes. I want to express what happens each minute

So what I want is to make new rows (in this case 4 since the charging lasts for 4 minutes) and divide the charging equally between the new rows. The third column is then not important as it is described now as number of rows.

Hope this clears things out, cause I would really appreciate help with this

Answer 1

[Steve Eddins]

One idea is to use a timetable and the retime function. Suppose I have the following matrix for a 4-minute charge and a 3-minute charge. (I won't be using your original third column since that information is duplicated by the difference between elements in the first column.)

>> x = [3849 1; 3853 2];

I'm going to add a final row to simplify the coding just a bit:

>> x = [x ; 3856 0]

x =

        3849           1
        3853           2
        3856           0

Now, make a timetable:

>> T = timetable(minutes(x(:,1)),x(:,2))

T =

  3×1 timetable

      Time      Var1
    ________    ____

    3849 min     1  
    3853 min     2  
    3856 min     0  

Adjust the second variable based on the charge duration:

>> T.Var1(1:end-1) = T.Var1(1:end-1) ./ minutes(diff(T.Time))

T =

  3×1 timetable

      Time       Var1  
    ________    _______

    3849 min       0.25
    3853 min    0.66667
    3856 min          0

Finally, use retime:

>> T2 = retime(T,'minutely','previous')

T2 =

  8×1 timetable

      Time       Var1  
    ________    _______

    3849 min       0.25
    3850 min       0.25
    3851 min       0.25
    3852 min       0.25
    3853 min    0.66667
    3854 min    0.66667
    3855 min    0.66667
    3856 min          0