Project - Data Handling and Interpolation

a = xlsread('VI.xlsx');
v = a(:,1);
i = a(:,2);
xv = [-17.3:0.1:0.9];
iq= interp1(v,i,xv);
iq1= interp1(v,i,xv,'spline');
figure(1);
plot(v,i,'o',xv,iq,':.');grid;xlabel('voltage');ylabel('ampere');
title('linear interpolation');
figure(2);
plot(v,i,'o',xv,iq1,':.');grid;xlabel('voltage');ylabel('ampere');
title('spline interpolation');
ampere1 = interp1(v,i,-17.2);
ampere2 = interp1(v,i,-13);
ampere3 = interp1(v,i,-11);
ampere4 = interp1(v,i,-9);
ampere5 = interp1(v,i,-6);
ampere6 = interp1(v,i,-1);
ampere7 = interp1(v,i,0.11);
ampere8 = interp1(v,i,0.25);
ampere9= interp1(v,i,0.5);
ampere10 = interp1(v,i,0.61);
ampere11 = interp1(v,i,0.66);
fid =fopen('C:\Users\Edwin fernandez\Desktop\ampere.txt','W');

fprintf(fid,'%f\n',ampere1);
fprintf(fid,'%f\n',ampere2);
fprintf(fid,'%f\n',ampere3);
fprintf(fid,'%f\n',ampere4);
fprintf(fid,'%f\n',ampere5);
fprintf(fid,'%f\n',ampere6);
fprintf(fid,'%f\n',ampere7);
fprintf(fid,'%f\n',ampere8);
fprintf(fid,'%f\n',ampere9);
fprintf(fid,'%f\n',ampere10);
fprintf(fid,'%f\n',ampere11);

fclose(fid);