1 files changed, 50 insertions, 0 deletions
diff --git a/260/DEPENDENCIES/cubicspline.sci b/260/DEPENDENCIES/cubicspline.sci
new file mode 100644
index 000000000..178a716eb
--- /dev/null
+++ b/260/DEPENDENCIES/cubicspline.sci
@@ -0,0 +1,50 @@
+function cubicspline(X,Y)
+   n = length(X);
+    //c(1) = 0;
+    //a = zeros(n-1,n-1);
+    for(i = 2:n-1)
+        c(i-1) = (6/(X(i+1)-X(i-1)))*((Y(i+1)-Y(i))/(X(i+1)-X(i)) - (Y(i)-Y(i-1))/                 (X(i)-X(i-1)));
+    end
+    for(i = 2:n-1)
+            a(i-1,i-1) = (X(i)-X(i-1))/(X(i+1)-X(i-1));
+            a(i-1,i)   = 2;
+            a(i-1,i+1) = (X(i+1)-X(i))/(X(i+1)-X(i-1));
+            
+    end
+[m,n] = size(a);
+
+b = a(:,2:n-1);    //For the case of natural splines, double derivative is zero at the first and last of data points. So removing the first and last columns since these are the only non-zero terms in the respective columns.
+
+//[r2 c2] = size(b);
+
+//disp(c)
+//disp(b)
+x  = inv(b)*c;
+
+//disp(x)
+x1(1,1) = 0;
+x1(n,1) = 0;
+x1(2:n-1,1) = x(:,1);
+
+printf('The values of second derivatives at the data points are :\n')
+disp(x1)
+
+x = poly(0,'x');
+
+for(i = 2:n)
+    f(i-1) = [Y(i-1)*(X(i)-x)/(X(i)-X(i-1)) + Y(i)*(x-X(i-1))/(X(i)-X(i-1))] + x1(i-1)/6*[(X(i)-x)^3/(X(i)-X(i-1))-(X(i)-X(i-1))*(X(i)-x)] + x1(i)/6*[(x-X(i-1))^3/(X(i)-X(i-1))-(X(i)-X(i-1))*(x-X(i-1))];
+end
+
+printf('\nThe expressions for the cubic splines are \n')
+disp(f)
+
+for(i = 1:n-1)
+    p = X(i):0.01:X(i+1);
+    q = horner(f(i),p);
+    plot(p,q)
+end
+plot(X,Y,'ks')
+xlabel('x')
+ylabel('y')
+
+endfunction
+\ No newline at end of file