From your post, what I understood is that you're trying to make linear interpolation of the imported data. I am not 100% sure if this is the case or not :). Anyhow, if this is what I guessed, here is a simple example code how to solve this exercise, e.g.:
[thrust_curve_values, output_value] = thrust_curve_function(t, FName);
plot(thrust_curve_values(:,1), thrust_curve_values(:,2), 'ro'), hold on
plot(t, output_value, 'k-')
legend('thrust_curve_values', 'inperpolated values')
function [thrust_curve_values, output_value] = thrust_curve_function(t, FName)
thrust_curve_values = readmatrix(FName);
t_values = thrust_curve_values(:,1);
F_values = thrust_curve_values(:,2);
output_value = interp1(t_values,F_values,t);
All the best