Data Set Functions - Overview

The functions discussed here are all under the Data dropdown button, except for the financial ones which are in the Mony list.

In addition to the memories M1 ñ M100, Napier also has a separate Data Set memory that can store up to 1000 values which can be manipulated inside Napier and read and written to text files. Since Napier stores all values including time as floating point numbers, the Data Set can be used for any value set.

The Data Set can be edited, sorted, entries added, multiplied, raised to a power of another value, and individual items used in other calculations. It can be averaged, both arithmetic and geometric, used in statistical functions, analyzed for percentiles, and used to calculate periodic portfolio returns given a series of balances. It also can be used to hold a series of cash flows to do Net Present Value and Internal Rate of Return calculations.

The Data Set can also be accessed from VBScript and can be saved and read back from files separately from the whole state. This allows you to keep several different sets of data and work on them in the same environment.

Data Entry, View, Edit

There are two main ways to load the Data Set from inside Napier, using the DataIn key, and entering a comma separated list of values then executing the DSto function.

DataIn Key

This is exactly the same as the ENTER key, but the results of each evaluation are appended onto the bottom of the Data Set. The information box will show you what Data Set entry you just entered and the value.

As with the ENTER key, if you are evaluating an expression which changes each time it is evaluated, repeatedly tapping DataIn will repeat the previous command as long as you donít edit the command.

Tab Separated Data List and the DSto Function

You can enter multiple values if you separate them with a comma, then either append them to the Data Set with the DataIn key, or replace the entire Data Set with the entries in the command box by using the DSto function. If you use the DataIn key, the result shown as an answer is the count of entries added to the Data Set.

 

Viewing the Data Set, DView and DEdit

With up to 1000 entries, it gets hard to remember them all, so DView will display a scrolling list of values. If you want to edit the entries, use the DEdit function, which will put a comma separated list of entries into the command box so you can edit them, then put them back into the Data Set with DSto.

Deleting the Data Set, DDel

To delete all entries, use DDel, but you canít reverse it, so be careful. In the File menu list, you can save the Data Set separately from the rest of the calculator state in a named file.

All The Data Set Functions

These are the functions under the Data dropdown:

DView
	Show data elements
Data
	Data(index) = item at index
	The first item is at index = 1
	The last item is at DCnt
DEdit
	Load the Data Set into the
	command line for editing.
	Items are comma separated, Can
	be edited, added or deleted
	After edit, reload  with DSto
DSto
	Replace data with comma sep list
	This deletes all current data
	and replaces it with the comma
	separated list in command line
DCnt
	Count of data items
Index
	Index(val) = closest item index
DDel
	Deletes all data elements
	Irreversibly deletes entire Data Set
DAdd
	Add answer to all items
	Uses current answer
	from command line and
	changes entire Data Set
DMul
	Multiply all items by answer
	Uses current answer
	from command line and
	changes entire Data Set
DPow
	Raise items to answer power
	Uses current answer
	from command line and
	changes entire Data Set
SortA
	Sort data ascending
	Changes entire Data Set
SortD
	Sort data descending
	Changes entire Data Set
Max
	Max value in data items
Med
	Max value in data items
MinD
	Min value in data items
Avg
	Arith average of data items
GAvg
	Geo average of data items
	Product of all items to the
	1/count power
AvDev
	Avg of abs deviations from mean
DProd
	Product of data items
DSum
	Sum of data items
PctlR
	PctlR(value)
	= percentile rank in data
	The percentile of the
	value relative to the data
PctlV
	PctlV(pctl)
	= value rel to data
	The value in the data for
	the input percentile
Kurt
	Kurtosis of Data Set
Skew
	Skew of Data Set
StdDev
	StdDev of data items
SqDev
	Sum of Sqs of deviations from mean
SumSq
	Sum of sq of data items
Var
	Variance of data items

Financial Functions that use the Data Set

These functions are under the Mony drop down key.

DNPV
		DNPV(i) = Data set NPV
		i: int rate. NPV of Data Set
		values as flows at reg intervals
		for an investment, value are +
		for flows in, - for flows out
		i is %, eg 8.5% is 8.5
DIRR
		Data set IRR
		IRR using the Data Set
		values as flows at reg intervals
		for an investment, value are +
		for flows in, - for flows out
		DIRR value is %, eg 8.5 = 8.5%
DTRtn
		Total return on data percents
		Data set should contain a set of
		periodic returns. This calculates
		the total return over all periods
		Entries are %, eg 8.5% is 8.5
DARtn
		Geo avg of data percents
		Data set should contain a set of
		periodic returns. This calculates
		the geometric average return
		Entries are %, eg 8.5% is 8.5
D2Rtn
		Convert Data Set to
		returns for each period. Set is
		sequential balances at regular
		periods, eg monthly, daily
		This replaces all the data with
		returns as %, eg 8.5% is 8.5
D2Bal
		Convert Data Set to
		balances for each period.
		Answer is starting amount
		Data set is sequential returns
		at regular periods, eg monthly
		Returns are %, eg 8.5% is 8.5
		This replaces all the data with
		balances for each period

Using RCnt

Under the Misc dropdown key, youíll find a function named RCnt which holds the repeat count. This is the count of the number of times ENTER or DataIn has been tapped between changes to the command box. This can be useful when working with the Data Set. If you use RCnt as the argument to the Data function, each time you tap ENTER without changing the command, the next Data Set value will be retrieved.

This can also be used with the value memories. As mentioned above, you can access the memories using the form M(n) where n is the number of the memory to retrieve. If you enter M(RCnt), then repeatedly tap ENTER, Napier will step through the value memories.

You can also use RCnt to generate a series of values. For example, if you want to see a set of small angle sin values, you could enter the expression:

Sin(.01 * RCnt)

Then tap DataIn repeatedly. This will append the series of sin values to the Data Set, starting at angle .01 and increasing by .01 for each entry. If you tap ENTER instead, youíll get the same results, they just wonít be saved anywhere, except for the last 10 in the automatically saved answer history list.

If you have a set of data such as grades or annual returns for a set of stocks, you can get the percentile rank of each in turn by entering the expression:

PctlR(Data(RCnt))

Then tap ENTER repeatedly to see the percentile value for each entry in turn. Whatís happening is that the Data(RCnt) inner expression returns each successive entry in the Data Set, which then is used by the PctlR function as the value to get the percentile for. You can use DataIn for this too, the percentile values will be appended to the end of the existing values in the Data Set.