Error using spline function???

Hello,

Kindly help me to solve this issue,

I am having 3 columns of values

nroll = totally 6289 values are in nroll (the values in nroll like -0.56894 -17.89654....)

time = totally 369 values are in time(in form of serial date number)

ulink = totally 369 values are in ulink(ranges from 1 to 4)

xx = spline(time,ulink,nroll)

my error is

Error using ./

Integers can only be combined with Integers of same class ,or scalar doubles.

Error in spline (line 58)

dd = ones(yd,1);dy = diff(x);divdif = diff(y,[],2)./dx(dd,:1);

So how to associate these values , what I mean is how to get particular nroll value for ulink corresponding to time...

[KSSV]

What is class of inputs?