title: Problem: Fehler in model.frame.default(formula = surv_mCRC ~ timing_6, data = list( : Variablenlängen sind unterschiedlich)
body: <p>I am new in R, mainly try to plot survival curves with ggsurvplot. Now I want to plot several curves in a row with ggsurvplot_by_group but get the error mentioned above. </p>
  
  <p>Follwing details:</p>
  
  <pre><code>str(dat_mCRC_df)
  'data.frame':   592 obs. of  24 variables:
   $ center      : chr  "OKL" "OKL" "OKL" "OKL" ...
   $ ED_num      : num  39874 39988 40183 40190 40191 ...
   $ sex         : chr  "männlich" "männlich" "weiblich" "männlich" ...
   $ age         : num  79 61 83 78 73 76 63 66 48 71 ...
   $ alive_death : num  1 1 0 1 1 1 1 1 1 1 ...
   $ mOS_m       : num  0 43 102 16 27 43 31 1 15 28 ...
   $ DFS_m       : num  30 43 17 16 0 33 13 0 8 0 ...
   $ dUICC_num   : chr  "3" "3" "2A" "3B" ...
   $ Lokalisation: chr  "Zäkum" "Flexura lienalis" "Colon ascendens" "Sigma" ...
   $ left_right  : chr  "right" "left" "right" "left" ...
   $ rectum_colon: chr  "Colon" "Colon" "Colon" "Colon" ...
   $ timing_6    : chr  "metachron" "metachron" "metachron" "metachron" ...
   $ timing_3    : chr  "metachron" "metachron" "metachron" "metachron" ...
   $ timing_12   : chr  "metachron" "metachron" "metachron" "metachron" ...
   $ met_res     : num  0 0 1 0 0 0 0 0 0 1 ...
   $ mHEP_only   : num  0 0 1 0 0 0 0 0 0 0 ...
   $ mHEP_PUL    : num  0 0 0 0 0 0 0 0 0 1 ...
   $ mPUL_only   : num  1 0 0 0 0 0 0 0 0 0 ...
   $ mOTHER      : num  0 0 0 0 0 0 0 0 0 0 ...
   $ RAS         : chr  "unknown" "unknown" "unknown" "RAS-wt" ...
   $ BRAF        : chr  "unknown" "unknown" "unknown" "unknown" ...
   $ MMR         : chr  "unknown" "unknown" "unknown" "unknown" ...
   $ met_loc     : chr  "PUL_only" "including LYM" "HEP_only" "including LYM" ...
   $ sex_num     : num  1 1 0 1 1 0 1 0 0 0 ...
  </code></pre>
  
  <p>than</p>
  
  <pre><code>
  
  &gt;surv_mCRC &lt;- Surv(dat_mCRC_df$mOS_m, dat_mCRC_df$alive_death)
  
  &gt;fit_mCRC_all &lt;- survfit(surv_mCRC~sex_num, data = dat_mCRC_df)
  
  &gt;ggsurvplot_group_by(fit_mCRC_all,dat_mCRC_df, group.by = "met_res",
                            palette = "lancet")
  
  </code></pre>
  
  <p>this results in:</p>
  
  <pre><code>Fehler in model.frame.default(formula = surv_mCRC ~ sex_num, data = list( : 
    Variablenlängen sind unterschiedlich (gefunden für 'sex_num')
  
  </code></pre>
  
  <p>which is `</p>
  
  <pre><code>error in model.frame.default(formula = surv_mCRC ~ sex_num, data = list( :variable 
                 lengths differ (found for 'sex_num')`
  
  </code></pre>
  
  <p>Possibly very easy for the most of you....
  Thanks for your help, regards</p>