Radians to RPM with diff(..) function

Hi...

I need to finde the RPM from a vector of radians and a vector of seconds (time).

I can do this manually by doing this:

rpmArray = (radiansArray/(2*pi));
minutesArray = timeArray/60;
slopeArray = [];

for counter = 1:length(minutesArray)    
    if counter < length(minutesArray)
        x1 = minutesArray(counter);
        x2 = minutesArray(counter + 1);
        y1 = rpmArray(counter);
        y2 = rpmArray(counter + 1);        
        slopeArray(counter) = (y2-y1)/(x2-x1);
    end       
end
slopeArray(end + 1) = slopeArray(end); % Fill in the missing entry

I can not figure out how to do this the "smart way" by using Matlabs diff().

Can anyone help me?

[Walter Roberson]

Perhaps use gradient() ?

[Kenneth Metzsch]

I think it gives me the same problem as diff().

It assumes spacing is 1.

Can you give me an example of how to overcome this?

[Stephen23]

"It assumes spacing is 1."

Did you look at the h/hx/hy inputs?

Answer 1

[Chunru]

rpmArray = (radiansArray/(2*pi));
minutesArray = timeArray/60;
slopeArray = gradient(rpmArray)./gradient(minuteArray);

[Kenneth Metzsch]

Thank you...it works

Actually it wil also work with diff() like this

rpmArray = (radiansArray/(2*pi));
minutesArray = timeArray/60;
slopeArray = diff(rpmArray)./diff(minutesArray);
slopeArray(end + 1) = slopeArray(end);