turning sporadic data points into regular ones

i have some data that represents purchases over time

it might look something like the below

DATE                        Value   item

jan 1                         5         spoon

jan 5                         5.2      spoon

jan 20                       5.3      spoon

feburary 10              5.4      spoon

April 10                    5.5      spoon

April 20                    5.6      spoon

I want to create data for every month that returns the most recent purchase.

DATE                        Value   item

Jan                           5         spoon

Feb                          5.3      spoon

Mar                         5.4      spoon

Apr                          5.4      spoon

May                         5.6      spoon

in practice the source data will have 20 different things (so not just the spoon) that we are buying so the value for each month is the most recent value specific to that item.

In case i am completly on the wrong track - the reason i am doing this is that I want to create a sort of 'Price Index' of all of these items and present them in a graph over time and I dont see an obvious solution with hte data as it is now.