linear Interpolation using matlab

Hi,

I am trying to interpolate using if loops. The time is in 30min intervals for 24hrs. I have attached the txt file that I am using, i have read the file in using

fid= fopen('ifng.txt','r');
format longg;
A = textscan(fid, ['%s', repmat('%f', 1 , 25)], 'HeaderLines', 1);
e= [A{2:end}];

So far I have

if(t<30)
    {E=((t-t0)/(t1-t0))*e1-((t1-t)/(t1-t0)e0)}
elseif(t<60)
    {E=((t-t1)/(t2-t1))*e2-((t2-t)/(t2-t1)e1)}
end

I am just wanting to know if I am along the correct lines or if I have missed out any steps. I know that the code isn't finished but just checking of I'm along the right lines as I am new to matlab.

Thanks