interpolation of data 2 vectors

hi i have trouble interpolate

Y=1945 1946 1947 1948 1949 1950 1951 1952 1953

L=6937 6976 6987 7015 9999 9999 6921 6958 6936

how I can interpolate these values of the year 1949 and 1950? and replace it in the L values. I know is a "for" but i dont know how implement it

Answer 1

[Walter Roberson]

Remove the points with bad data . interp1() the points back in

interp1(Y2, L2, [1949 1950])

[David Lopez]

thanks but how is the sintaxis for bad data?

[Walter Roberson]

is_bad = (L == 9999);

Lfixed = L;

Lfixed(is_bad) = interp1( Y(~is_bad), L(~is_bad), Y(is_bad) );