# How to compute CDF for Lognormal distribution survival formula

I would like to manually compute the lognormal distribution but I am not clear on how to compute the CDF value that is required in the formula for the Survival function.

The formula is as below:

$$S(x)=1−Φ(\frac{ln(x)}{σ})$$

Is there a way to get this value using R?

Thanks

• so far what I have done is to use this formula in R: S(t) = 1 - plnorm(log(t) / model$scale) . Is this correct? – MugB Nov 13, 2019 at 13:16 • Why doesn't$\mu\$ appear in your formula? Nov 14, 2019 at 2:56
• okay i found this link: stats.stackexchange.com/questions/33664/… with another formula. Does this mean that the μ comes from the survreg function?
– MugB
Nov 14, 2019 at 9:21
• it shows from this link: blogs2.datall-analyse.nl/2016/02/17/… that the mu is taken from coef of the survreg function. Is this correct?
– MugB
Nov 14, 2019 at 12:57
• Sorry, wasn't able to post this yesterday -- I eventually figured out that the point of the non-mu formula is just as a "standard" form of lognormal with median 1, which you might treat as a multiplicative error term. In that case, yes, the mean survival (conditional on the predictors) would supply the mu that this would represent the variation around. Nov 15, 2019 at 13:44

$$S(t) = 1 - plnorm(t, meanlog, sdlog)$$