How to code a ramp function?

Hi,

I tried to code a ramp function as attached herewith.

But getting an error

"Operands to the logical AND (&&) and OR (||) operators must be convertible to logical scalar values. Use the ANY

or ALL functions to reduce operands to logical scalar values."

Hence I need your valuable suggestion so as to run the same.

function r = ramp(t)
tstep = 10; 
tmin = 0;
tmax = 10;
t = linspace(tmin,tmax,tstep);

if t<=4 
    H0=0.2*t;
   
end

if t>=5 && t<=7
    H0=max(0,t);
    
end   

if t>=8
    H0=0.2*t;
end    
plot(H0,t)

with regards,

rc

Answer 1

[Walter Roberson]

t = linspace(tmin,tmax,tstep);

t is a vector.

if t<=4 

MATLAB treats that as equivalent to

if all(t<=4)

and the body of the if would be executed only if no entries in t are greater than 4. But with the particular values you used for linspace() there are some values greater than 4 in t, so the if would fail.

if t>=5 && t<=7

That would be treated like

if all(t>=5 && t<=7)

which would fail for vector t because && can only be used with scalars. If you had coded

 if t>=5 & t<=7

then the & operation could succeed, returning a vector of values, and the statement would be equivalent to

if all(t>=5 & t<=7)

but that would fail beause there are some values outside that range.

        H0=0.2*t;

That would take all of the vector t and multiply by 0.2, and asssign the vector result to H0. But that is not going to be assigning those values to H0 selectively according to which elements in t are <= 4.

You need to proceed by using a for loop, or by putting the code into a function and using arrayfun so that you never pass in a non-scalar value. Or you need to learn how to use logical indexing. https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html