% script Global_Temperature. Analyze NASA data
% relative to the surface overall temperature anomaly
% in the period 1955 - 2000.
% Anomaly is computed respect to the average of the
% period 1951-1980.
% Data can be downloaded from

% https://climate.nasa.gov/vital-signs/global-temperature/
%
clf
t = (1955:5:2000)';
y = [-0.0480; -0.0180; -0.0360; -0.0120; -0.0040; 0.1180; 0.2100; 0.3320; 0.3340; 0.4560];
plot(t,y,'.','Markersize',12), ylabel('Temperature Anomly in Celsius')
pause
t_scal = (t-1950)/10;  % time expressed in decades starting from 1950
% plotting grids
tt = linspace(1955,2000,100);
tt_scal = (tt-1950)/10;
%
% grado = length(t)-1;   % interpolation
degreepol = 3;    % least squares with cubic polynomial
cc = polyfit(t_scal,y,degreepol);
hold on
plot(tt,polyval(cc,tt_scal))
title('global surface temperatur anomaly')
%  alternative plot
%p = @(x) polyval(cc,(x-1950)/10);
% fplot(p,[1955 2000])
hold off