Does anyone have any idea what the big I in this

equation is?

**3.2. .Prediction Markets for Logistic Regression**
A variant of logistic regression can also be modeled using prediction markets, with the following betting functions:

. . . . .[tex]\phi_m^1(\mbox{x},\, 1\, -\, c)\, =\, (1\, -\, c)\left(x_m^+\, -\, \dfrac{1}{B}\ln(1\, -\, c)\right)[/tex]

. . . . .[tex]\phi_m^2(\mbox{x},\, c)\, =\, c\left(-x_m^-\ -\, \dfrac{1}{B}\ln(c)\right)[/tex]

where [tex]x^+\, =\, xI(x\, >\, 0),\, x^-\, =\, xI(x\, <\, 0),\, [/tex] and [tex]B\, =\, \sum_m \beta_m.[/tex]

I can't for the life of me figure it out, and can't find a prior reference in the article. Thanks.

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