Create a vector in 15-minute intervals (from 0 am to 24 pm)

Hi everyone!

I need to create a bar graph with the x axis in 15-minute intervals (from 0 am to 24 pm). Can someone help me to create a vector to do this with HH:MM on the plot?

Answer 1

[Walter Roberson]

Sure, you can xticks() with datetime objects if you have a datetime ruler.

The problem is being able to read it. Every 15 minutes for a day is 96 ticks.

Though for your purposes, perhaps just leaving out the xticks() call on this example would be enough for your purposes.

BT = datetime('yesterday')

BT = datetime
   12-Jun-2021

T = BT + minutes(sort(1440*rand(1, 500)));
T(1:10)

ans = 1×10 datetime array
   12-Jun-2021 00:03:05   12-Jun-2021 00:03:54   12-Jun-2021 00:03:56   12-Jun-2021 00:04:57   12-Jun-2021 00:07:07   12-Jun-2021 00:15:35   12-Jun-2021 00:23:47   12-Jun-2021 00:23:58   12-Jun-2021 00:24:00   12-Jun-2021 00:27:15

V = rand(size(T))

V = 1×500

0.9208 0.8995 0.6975 0.5460 0.2480 0.6074 0.6270 0.5911 0.8992 0.7790 0.8939 0.5660 0.9413 0.7454 0.2384 0.5734 0.3513 0.5612 0.8775 0.7663 0.3734 0.7775 0.0866 0.8703 0.9714 0.2642 0.8139 0.0315 0.7880 0.0938

ticks = BT + minutes(0:15:1440);
Vdis = accumarray(discretize(T(:), ticks), V(:), [length(ticks),1]);
bar(ticks, Vdis)
xticks(ticks)

[Walter Roberson]

See also retime() for which you can use counts or sum or mean or whatever is appropriate for your circumstances.

[Steven Lord]

I'd consider creating ticks for every 15 minutes but only adding labels to the hourly ticks.

x = minutes(0):minutes(15):hours(24);
v = minutes(x);
plot(x, sind(v));
% Ticks every 15 minutes
xticks(x)
% Labels every 60 minutes
L = repmat("", size(x));
L(1:4:end) = string(x(1:4:end));
xticklabels(L)
xtickangle(90)

[Renan Santos]

Thanks for all, but I'd like to know if there is any way to do it running in MATLAB 2014 R2014a.

In this version doesn't have functions like minutes, datetime, etc.

[Walter Roberson]

as_minutes = 0:15:(24*60)-1;
as_days = as_minutes ./ (24*60);

y = rand(size(as_days));   %something to plot

plot(as_days, y);
datetick('x', 'HH:MM')