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function y = ei(x) %EI 1-argument exponential integral function. % Y = EI(X) is the 1-argument exponential integral. It is defined % as: % % EI(x) = integral from -Inf to x of exp(t)/t dt % % See also EXPINT, SYM/EXPINT. % Copyright 2012 The MathWorks, Inc. y = sym.useSymForNumeric(@ei, x);