title: How to fix an error with zero-inflated Poisson regression
body: <p>I ran zero-inflated Poisson regression with package <code>pscl</code> and came across a same error with this <a href="https://stats.stackexchange.com/questions/96010/zero-inflation-on-steroids-choose-among-poisson-negative-binomial-and-zero-inf">post</a> </p>
  
  <p>However, since I know there is a separate process for excess zeros indicated by <code>z</code>, does it still make sense to just run Poisson as a solution (Poisson results are just fine)? Is there an alternative way to fix this problem for ZIP? I also tried zero-inflated negative binomial regression but it got the same error. Thanks.</p>
  
  <pre><code>Call:
  zeroinfl(formula = y ~ x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9 | z, data = df)
  
  Pearson residuals:
       Min       1Q   Median       3Q      Max 
  -2.48465 -0.06156 -0.06126 -0.06091  5.57840 
  
  Count model coefficients (poisson with log link):
                   Estimate Std. Error z value Pr(&gt;|z|)
  (Intercept)      3.547e+00         NA      NA       NA
  x1              -3.251e-02         NA      NA       NA
  x2               6.290e-03         NA      NA       NA
  x3               8.867e-01         NA      NA       NA
  x4               1.432e-01         NA      NA       NA
  x5               2.705e-01         NA      NA       NA
  x6              -8.223e-10         NA      NA       NA
  x7              -7.218e-02         NA      NA       NA
  x8               3.322e-02         NA      NA       NA
  x9              -2.072e-01         NA      NA       NA
  
  Zero-inflation model coefficients (binomial with logit link):
              Estimate Std. Error z value Pr(&gt;|z|)
  (Intercept)    5.531         NA      NA       NA
  z              158.108         NA      NA       NA
  Error in if (getOption("show.signif.stars") &amp; any(rbind(x$coefficients$count,  : 
    missing value where TRUE/FALSE needed
  </code></pre>