DM41 Save/Restore Statistics

Using Extended Memory to save Statistics Registers

Statistics use 6 regular registers to keep track of data for calculating Mean and Standard Deviations.

Keeping a long-term record of a set of variables means not being able to use the Statistics functions for anything else unless steps are taken to save and restore the registers.

It is possible to save the 6 registers in a data file in Extended Memory and then use the statistics for other things, and restore the saved Statistics back to Main Memory when required.

By Default the Statistics registers start at R11 but this can be changed with the command ∑REG

This is the default list of Statistics Registers and contents

Advantage Pac : CFIT application seems to reset ∑REG to 12

The statistics registers use 6 Main Memory registers, usually R11 → R16

We need to create a Data File in Extended Memory to hold these.

• Put the name in ALPHA e.g. REGS
• Put 6 in x register
• excecute CRFLD to create the Data File REGS in Extended Memory

Once it's created it can be used to hold the contents of the 6 Statistics Registers

• We need to make sure our Data File is the current file and that the pointer is at the beginning of the file
  • Put REGS in ALPHA
  • Put 0 in X so that we put the pointer at the first register record in the data file.
  • Execute SEEKPTA
• Now we need to copy the 6 Registers R11 → R16 to the Data File REGS
  • ensure REGS is still in ALPHA
  • put a number in X to indicate which range of Registers to save, this is bbb.eee where b is the beginning register and e is the end
    • put 11.016 in X
  • execute SAVERX

• We need to make sure our Data File is the current file and that the pointer is at the beginning of the file
  • Put REGS in ALPHA
  • Put 0 in X
  • Execute SEEKPTA
• We can copy the 6 registers held in the Data File REGS back to R11 → R16
  • ensure REGS is still in ALPHA
  • put a number in X to indicate where the recovered registers will be put in Main Memory
    • put 11.016 in X
  • execute GETRX

It is possible to change the base register of the 6 Statistics Registers, away from the default of R11.

We need to take this into account.

This uses the query ∑REG? to find the base register, then create bbb.eee using simple arithmetic.

When used in SAVER (saveRegs) we ensure we copy the current Statistics Registers data.

When used in GETR (getRegs) we ensure we restore our data to the Registers currently set to be the active Statistics Registers (they may have changed since first saving them)

LBL ¬SAVER
¬REGS
0
SEEKPTA
∑REG?
1.001
*
.005
+
SAVERX
¬REGS SAVED
AVIEW
PSE
CLD
RTN
LBL ¬GETR
¬REGS
0
SEEKPTA
∑REG?
1.001
*
.005
+
GETRX
¬REGS OK
AVIEW
PSE
CLD
RTN

It's possible to have more than one Extended Memory file with Stats registers.

This could keep track of different sets of statistics and allow restore, update, save for many sets of statistical data.

I've set up two data files : REGS and CHESS in extended memory and made two version of the simple program above, the only change is to alter the lines which put the name of the file in ALPHA

Then I thought of adding a 7th Register holding the DATE of the latest SAVE for the CHESS statistics, so I can keep track of whether I'm up to date in entering the scores.

Delete the original CHESS Data File & make a new one with 7 registers

• ALPHA → CHESS
• execute PURFL
• X = 7
• ALPHA still → CHESS
• execute CRFLD to create the new 7-register data file

The date is automatically stored in the register just after the Stats - in general in R18 when ΣREG is 12 - and automatically adapts the register used depending on ΣREG?

Here is SAVEC and GETC for saveChess and getChess

LBL ¬SAVEC
¬CHESS
0
SEEKPTA
∑REG?
STO 01
6
+
STO 00
DATE
STO IND 00
RCL 01
1.001
*
.006
+
SAVERX
¬CHESS SAVED
AVIEW
PSE
CLD
RTN
END

LBL ¬GETC
¬CHESS
0
SEEKPTA
∑REG?
STO 01
6
+
STO 00
RCL 01
1.001
*
.006
+
GETRX
CLA
RCL IND 00
¬LAST 
ADATE
AVIEW
PSE
CLD
RTN
END

I might make a better version which prompts for a Data File name rather than having one separate program for each scenario