title: R effects package Error: non-conformable arguments
body: <p>I am using <code>effects</code> R <a href="http://cran.r-project.org/web/packages/effects/index.html" rel="nofollow">package</a> and <code>effect</code> function on a cox model. There is a default method for this function so it somehow should work for any model. </p>
  
  <p>When I try to use this function I get this error: </p>
  
  <p><strong>Any idea how to fix this and what is wrong?</strong></p>
  
  <pre><code>&gt; eff_cf &lt;- effect("TP53:MDM2", model)
  Error in mod.matrix %*% mod$coefficients[!is.na(coef(mod))] : 
    non-conformable arguments
  </code></pre>
  
  <p>My model looks like this:</p>
  
  <pre><code>&gt; model
  Call:
  coxph(formula = Surv(times, patient.vital_status) ~ TP53 + MDM2 + 
      TP53:MDM2, data = clinForPlot)
  
  
                                  coef exp(coef) se(coef)      z       p
  TP53Other                     -0.163     0.850    0.217 -0.752 4.5e-01
  TP53WILD                      -1.086     0.337    0.277 -3.928 8.6e-05
  MDM2(1183.7,1674.7]           -0.669     0.512    0.235 -2.851 4.4e-03
  MDM2(1674.7,2248.5]           -0.744     0.475    0.305 -2.444 1.5e-02
  MDM2(2248.5,50339]            -0.867     0.420    0.375 -2.308 2.1e-02
  TP53Other:MDM2(1183.7,1674.7]  0.394     1.483    0.412  0.958 3.4e-01
  TP53WILD:MDM2(1183.7,1674.7]   0.133     1.142    0.413  0.323 7.5e-01
  TP53Other:MDM2(1674.7,2248.5] -0.192     0.825    0.517 -0.372 7.1e-01
  TP53WILD:MDM2(1674.7,2248.5]   0.546     1.726    0.433  1.260 2.1e-01
  TP53Other:MDM2(2248.5,50339]  -0.140     0.869    0.650 -0.215 8.3e-01
  TP53WILD:MDM2(2248.5,50339]    0.786     2.195    0.484  1.623 1.0e-01
  
  Likelihood ratio test=72.8  on 11 df, p=3.54e-11  n= 1321, number of events= 258 
  </code></pre>
  
  <p>And the model and the data.frame used for model can be reproduced using this code</p>
  
  <pre><code>library(archivist)
  model &lt;- loadFromGitub("68eeefba87be70364eb3801cec58eb3d", 
                user = "MarcinKosinski",
                repo = "Museum",
                value = TRUE)
  
  clinForPlot &lt;- loadFromGitub("cfa5145e6b98964d5f8b760bf749e426", 
                         user = "MarcinKosinski",
                         repo = "Museum",
                         value = TRUE)
  </code></pre>
  
  <p><strong>Any idea how to fix this and what is wrong?</strong></p>