algorithm for calculating a running clicks/second value (ala a speedometer) - c++

Question

I'm trying to figure out how to produce a running calculation of clicks per second (e.g. an app with a window I click on and it gives me a speedometer-like value of the 'speed' of my clicks in clicks per second). For some reason the algorithm is eluding me.
It's easy to figure out if I just want to figure out clicks per second if at each second I report how many clicks happened in the last second. But where it gets tricky is if there was one click in second 1, then 0 clicks in seconds 2-9 and 1 click in second 10. Presumably that would be .2 clicks per second--although really only if it was kept up and averaged out to that over time. If that click in second 10 was followed by 0 clicks for 40 seconds, then it should be 0 clicks/second, not .04 clicks/second.
So clearly I need some kind of window within which I'm willing to presume the clicks are part of a pattern, or at least associated with the last ones. But it's just not making sense to me.
I'm using openframeworks for this, so have an update() function that is called more than once/second (say 30x/sec), and have a mousePressed() function that allows me to increment a variable to track the clicks. i can use difftime() and time() to track whether I just crossed into a new second, and then use fmod() to figure out if I just crossed some larger interval.
Any suggestions are appreciated.

Answer 1

I think you want to calculate the running average of the clicks per second. You would use a circular buffer of counters of a length of say 30 for a 30 second window. The average clicks per second is the sum of the counters divided by 30.
An index points to the current counter, the index is incremented modulo 30 every second, and the counter at the new position is set to zero.
example:
const unsigned BUFFER_SIZE = 30;
unsigned counters[BUFFER_SIZE];
unsigned current = 0;
time_t last;
void init() {
time(&last);
}
void update() {
time_t now;
time(&now);
while (now - last >= 1) {
++last;
current = (current+1)%BUFFER_SIZE;
counters[current] = 0;
}
}
void mousePressed() {
++counters[current];
}
float average() {
float sum = 0;
for (int i = 0; i < BUFFER_SIZE; ++i) {
sum += counters[i];
}
return sum/BUFFER_SIZE;
}

Answer 2

This is pseudo code, but I think it will do what you are asking:
onUpdate() {
if (currentTime() - lastClickTime > idleTimeout) {
// reset the clickometer to zero
} else {
// calculate the speed
}
}
onMouseClick() {
lastClickTime = currentTime();
// and whatever else needs to happen
}
Basically you are just tracking the time of the last click, and making sure it happened within the idleTimeout, which you obviously have to define for some span of time.