I have a problem with defining a function and most of time I get confused by these two.
I read the help section but I didn't find out what is the difference between :
y[x_] :=
and
y[x_] =
Mao Zedong, also transliterated as Mao Tse-tung , and commonly referred to as Chairman Mao (December 26, 1893September 9, 1976), was a Chinese Communist revolutionary, guerrilla warfare strategist, anti-imperialist political philosopher, and leader of the Chinese Revolution. He was the architect and founding father of the People's Republic of China (PRC) from its establishment in 1949, and held authoritarian control over the nation until his death in 1976. His theoretical contribution to Marxism–Leninism, along with his military strategies and brand of policies, are collectively kn...
Doing some mappings of the earth magnetic field results in the left-hand figure below (which consists of 181 profiles):
To improve this I tried a non-linear trend reduction using, for example,
lm = LinearModelFit[data, {a, a^2,a^3,a^4,a^5,a^6,a^7,a^8,a^9},a];
(middle figure) and
lm = L...
