It is possible to plot a graph of values kept over a period of time using the Diary Measurement Graph option from the menu. Firstly choose Add diary measurement type from the Calendar menu. You should give a name, a colour (using the JEAN colour picker) and the number of decimal places to which the measurement value should be kept. For instance, you may want to measure room temperature over a period of time and hold the value to two decimal places.
With a day selected, you can then Set diary measurement. A dialogue box will appear with the names of the measurement types you have already set up. Once you have set the values for that day, these will appear in a separate section in the diary.
You can then create a histogram of these values. The bars will be displayed in the colours you picked for that measurement type and can be plotted side by side on the same graph or separately. JEAN will work out appropriate values for the y-axis from the minimun and maximum values you have entered.