MATLAB: Interpt 1 is giving me error

Question

x_i = [25 27 29]
y_i = interpt1(t(7:10),log10(C(7:10)),x_i,'linear','extrap');
figure;
plot(T,C,'-r');
hold on;
plot(x_i,10.^y_i,'--*');
figure;
semilogy(T,C,'-*');
hold on;
semilogy(x_i,10.y^i,'--o');

Answer 1

The function name is interp1 not interpt1