What did I do wrong with this funtion? - Implementing msplines and isplines in Octave

[Corrado]

Dear friends,

I am trying to implement in Octave the two spline families as in the 
documentation here below attached. I am a newbie to Octave, and this is my 
first function.

I built the function:

function retspline = mspline (i,x,k,t)
        # i is the spline index in the family
        # x is the variable
        # t is the vector of knots, t(h) is the h-th knot
        # k is the Mspline degree
        
        I=i
        
        if(k==1)
                
                if(x<t(i+1) & x>=t(i))
                        td=t(i+1)-t(i)                          
                        M=1/td                  
                else
                        M=0
                endif

        else    
                
                kk=(k-1)
                
                if (x>=t(i) & x<t(i+k))
                        M=k*((x-t(i))*mspline(i=I,x=x,k=kk,t=t)+(t(i+k)-
x)*mspline(i=(I+1),x=x,k=kk,t=t))/((k-1)*(t(i+k)-t(i)))
                elseif (x<t(i) | x>=t(i+k))
                        M=0
                endif

        endif
                
        retspline=M     

endfunction

but for some reason it does not work ....

I add that I am a newbie with Octave, please do not shut me.

What did I do wrong?

Best,
-- 
Corrado Topi

Global Climate Change & Biodiversity Indicators
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: address@hidden

mspline
Description: PNG image

ispline.png
Description: PNG image