DLMF:

Figure 6.3.3 (See in context.)

Figure 6.3.3: $|\mathop{E_{1}\/}\nolimits\!\left(x+iy\right)|$ , $-4\leq x\leq 4$ , $-4\leq y\leq 4$ . Principal value. There is a cut along the negative real axis. Also, $|\mathop{E_{1}\/}\nolimits\!\left(z\right)|\to\infty$ logarithmically as $z\to 0$ .

Annotations:

Symbols:: $\mathop{E_{1}\/}\nolimits\!\left(z\right)$ : exponential integral, $x$ : real variable and $z$ : complex variable
Keywords:: exponential integrals
Permalink:: http://dlmf.nist.gov/6.3.F3.mag
Encodings:: Magnified png, VRML, X3D, pdf