Fit poisson distribution to data (histogram + line)
<p>I need to do exactly what @interstellar asked here <a href="https://stackoverflow.com/questions/38249508/fit-poisson-distribution-to-data">Fit poisson distribution to data</a> but within the R environment (not matlab).</p>

<p>So, I created a barplot with my observed values and I just need to fit a poisson distribution on it.</p>

<p>Here my data:</p>

<pre><code>df = read.table(text = 'Var1 Freq     
    6    1
    7    2
    8    5
    9    7
   10    9
   11    6
   12    4
   13    3
   14    2
   15    1', header = TRUE)
</code></pre>

<p>the barplot created is the following:</p>

<pre><code>t = barplot(df$Freq, ylim = c(0,10))
axis(1, at=t, labels=df$Var1)
</code></pre>

<p>I am still new to R so how I could use the <code>fitdist</code> function or something else to create a line above my barplot?</p>

<p>Any help would be really appreciated.</p>

<p>UPDATE</p>

<p>I have worked out something but I am not sure 100% if it is correct:</p>

<pre><code>#create barplot
t = barplot(df$Freq, ylim = c(0,10))
axis(1, at=t, labels=df$Var1)

#find lambda value from my data
pois = fitdist(df$Freq, 'pois', method = 'mle')
print(pois)

#result
Fitting of the distribution ' pois ' by maximum likelihood 
Parameters:
       estimate Std. Error
lambda        4  0.6324555

#create 10 values from a real poisson distribution
dist = dpois(1:10, lambda = 4)

#multiply them by `sum(df$Freq)` in order to scale them to the barplot
dist = dist * sum(df$Freq)

#add the line plot to the original barplot
lines(dist, lwd = 2)
</code></pre>

<p><a href="https://i.stack.imgur.com/XaEJ9.png" rel="nofollow noreferrer">result</a></p>

<p>However, the curve is not smooth..</p>