plotting graph involving converting time intervals

I have a large number of time values that start at a large number of milliseconds and increase with equal interval, along with an equal amount of speeds. I am looking to plot a graph with the x axis having the time values with interval of one day and starting at day 1 and the y axis having an equal amount of plots for speed. Any ideas?

[Mathieu NOE]

hello

sounds to me like you want to pick only data at one day interval from your milliseconds sampled data

this can be simply achieved by interpolation using interp1

[Peter Perkins]

Max, your description is not very clear. You need to give a short clear example of what you have and what you want the plot to look like.

Answer 1

[Abhishek Chakram]

Hi Max Fairhurst,

It appears to me that you want to plot milliseconds with equal interval of a day, along with an equal amount of speeds. For this, you can use the “plot” and “datetick” functions. Here is an example for the same:

% Convert time values from milliseconds to serial date numbers
t = t / (24 * 60 * 60 * 1000); % divide by the number of milliseconds in a day
t = t + datenum (0); % add the serial date number for January 0, 0000

% Plot speed values against date numbers
plot (t, s)
xlabel ('Time (days)')
ylabel ('Speed')

% Format x-axis tick labels as days
datetick ('x', 'keeplimits', 'keepticks')

You can refer to the following documentation to know more about the functions used:

• datetick: https://www.mathworks.com/help/matlab/ref/datetick.html
• plot: https://www.mathworks.com/help/matlab/ref/plot.html

Best Regards,

Abhishek Chakram

[Peter Perkins]

datenum and datetick are no longer the recommended way to make plots vs. time.

The fact that you had to do this

t = t + datenum (0); % add the serial date number for January 0, 0000

should suggest that there's a better way. That way is to use durations.