Calculate difference in sum based on previous day, week, month,year

[varmekontrol]

Hi

I need help on how to find the consumption of a heat meter based on the previous date. 

My Data

Meter No]	Created	Energy (wH)	What i need
82251145	17-03-2019	100
82251145	18-03-2019	250	150
82251145	19-03-2019	500	250
82251145	20-03-2019	1200	700
82251145	21-03-2019	5000	3800
82251145	22-03-2019	6000	1000
82251145	23-03-2019	8500	2500
82251145	24-03-2019	9500	1000

My load.

Heat_meter:
LOAD 
     Num(@2) as [Meter No], //Heat meter serial no. 
     Date(@3) as [Created], //Timestamp
     Num(@7) as [Energy (wH)] //Actual energy used since the day it was installed. 

//What i need is to subtract the Energy from the previous day, to get the consumption used the last day. 

FROM
[D:\Elvaco_FTP\Elvaco_Teknikrum\HeatMeter\*.csv]
(txt, codepage is 28591, no labels, delimiter is ';', msq, header is 1 lines where Date(@3)>=today()-7;

[Vegar]

Heat_meter:
LOAD 
     Num(@2) as [Meter No], //Heat meter serial no. 
     Date(@3) as [Created], //Timestamp
     Num(@7) as [Energy (wH)], //Actual energy used since the day it was installed. 
     Num(@7 - peek('@7') as [What i need]

FROM
[D:\Elvaco_FTP\Elvaco_Teknikrum\HeatMeter\*.csv]
(txt, codepage is 28591, no labels, delimiter is ';', msq, header is 1 lines where Date(@3)>=today()-7;
 

Read about peek() here: 

https://help.qlik.com/en-US/qlikview/November2018/Subsystems/Client/Content/QV_QlikView/Scripting/In...

[Vegar · Accepted solution]

Heat_meter:
LOAD 
     Num(@2) as [Meter No], //Heat meter serial no. 
     Date(@3) as [Created], //Timestamp
     Num(@7) as [Energy (wH)], //Actual energy used since the day it was installed. 
     Num(@7 - peek('@7') as [What i need]

FROM
[D:\Elvaco_FTP\Elvaco_Teknikrum\HeatMeter\*.csv]
(txt, codepage is 28591, no labels, delimiter is ';', msq, header is 1 lines where Date(@3)>=today()-7;
 

Read about peek() here:

https://help.qlik.com/en-US/qlikview/November2018/Subsystems/Client/Content/QV_QlikView/Scripting/In...

[varmekontrol]

(Jeg siger tak for hjælpen, det var lige det jeg skulle bruge. :))

Just a msg. for my Scandinavian buddy 🙂
The Peek() was just what i needed. 

This is my result if someone else needs the solution. 

Heat_meter_temp:
LOAD Cme_no, 
     Meter_no, 
     date(Created, 'YYYY-MM-DD HH:MM:ss') as Created,
     num(Energy_wH/1000) as Energy_wH, 
     Volume_m3, 
     Volume_flow_m3H, 
     Flow_temp_C, 
     Return_temp_C, 
     Temp_diff_C
FROM
[C:\Heat_meter.qvd]
(qvd);

Heat_meter: 
NoConcatenate
LOAD *,
	 peek('Energy_wH') as Energy_wH_peek,
	 ((Energy_wH-peek('Energy_wH'))) as Energy_wH_consumption,
	 peek('Volume_m3') as Volume_m3_peek,
	 num(((Volume_m3-peek('Volume_m3'))),'##,00') as Volume_m3_consumption
Resident 
Heat_meter_temp order by Meter_no,Created;

Drop Field Energy_wH_peek, Volume_m3_peek;
Drop Table Heat_meter_temp;