How to plot serial data against time

I have an arduino sending serial data every 2 seconds to the serial monitor and Matlab code will read from that serial monitor and plot a graph. The graph plots a value every 2 seconds but how do i make the x -axis equal to time so that the graph shows data is plotted every 2 seconds.

Answer 1

[dpb]

In real time or just 2-second intervals? If the former see

doc now
doc datetick
doc datenum

If just incremental seconds, just increment a t vector by 2 and use it for the x-axis values.

Note the example in the doc's on animation in the Graphics 2D/3D plots section to do this more efficiently that repetitively calling plot

[Jack]

thank you, ill just increment a t vector by 2 and use it for the x-axis values. But If im taking multiple readings at different time intervals how do i plot it at real time; datetick and datenum both require a date parameter but i just want seconds

[dpb]

Again, that depends on what specific seconds you mean...if it's seconds since the first reading, just subtract that original now value t0 from each current time and then format to seconds.

Altho there you'll probably want to keep the differential as numeric and scale externally because datestr and friends will wrap the SS field modulo 60.

If it's the actual seconds of wall clock when the data were collected, then use the datenum as is but simply format the time portion. Try

for i=1:5,fprintf('%3s',datestr(now,'SS')),pause(2);end,fprintf('\n')

at command line...