Vectorizing for loop for faster processing

I have a column of sorted row numbers labelled "Row Numbers"

Row Numbers =

1

3

5

8

100

...

...

I want to use information from Row numbers to sort a table labbeled "Table" into different sections

Table =

Time SensorOut

1:00 1

2:00 3

3:00 2.3

4:00 3.4

5:00 3.1

6:00 30

7:00 3

8:00 3

9:00 3

... ...

... ...

... ...

What i want to achieve is this

Table =

Time SensorOut Section

1:00 1 1

2:00 3 1

3:00 2.3 2

4:00 3.4 2

5:00 3.1 3

6:00 30 3

7:00 3 3

8:00 3 3

9:00 3 4

... ... ...

... ... ...

... ... ...

What i have done so far

for i = 1:length(rownumbers)-1
    Table.Section(rownumbers(i):rownumbers(i+1)) = i;
end

This works but the issue is that i have 100,000 rows of data and each loop is taking about 0.4 seconds. I was wondering if any one had an idea how to vectorize this for loop for faster processing? Or a more clever way of achiveing this?

Answer 1

[AndresVar]

You defined bin edges so you can try discretize: Group data into bins or categories - MATLAB discretize (mathworks.com)

idx=1:10

idx = 1×10

1 2 3 4 5 6 7 8 9 10

rowNums=[1 3 5 8 inf]

rowNums = 1×5

1 3 5 8 Inf

discretize(idx,rowNums)'

ans = 10×1

1 1 2 2 3 3 3 4 4 4