okay we are almost there ready for chart
number three I hope you are here we go
in this lesson we would like to create a
chart that gives us information about
the ratio between reviews left and the
number of audiobook purchases in a given
month an important KPI showing us
whether people who buy audiobooks leave
reviews to do that will need to create a
few calculator fields
first let's create a field which counts
the number of ratings not the sum of all
ratings but there count it will be much
easier if we create this field and use
it going forward
the name of the field we are creating is
number of ratings and I simply need to
use the count function the next
calculated field I would like to create
is number of purchases let's change the
data source we've selected to audiobook
sales here I will create a field called
number of purchases which will contain
the number of audiobook sales the
company made how do I count the number
of purchases well the transaction ID
code is unique right if we count it we
should obtain the number of sales
transactions which is precisely what we
are looking for okay good we are almost
ready now we can create the last
calculated field which will be the ratio
between reviews and new purchases let's
do that it is a fairly easy task given
that we've already created the number of
reviews and the number of purchases all
we have to do is divide the two figures
and will obtain the measure we want to
plot from the very beginning let's add
it to the rows of our visualization the
result is a pretty nice bar chart which
is a bit too large but still looks
meaningful it appears that the ratio of
ratings to new students was
significantly lower in November 2017 and
way higher the month before
three times lower to be precise I am
sure the firm's business intelligence
team would want to have a look at that
and analyze what the reason is for this
let's quickly edit the title of the
horizontal axis to month and save our
work in our next lesson we'll organize
the charts we created in a dashboard
stay tuned and thanks for watching