Multiply array if number is under certain value

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Peter Lyngbye 2022-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/1677489-multiply-array-if-number-is-under-certain-value

评论： Mathieu NOE 2022-3-22

Im using a script to calculate power from two varaiables. Though i need to multiply my power (P_out) with a certain value (for example 2) if the value is under 1.000.000 to correct my data...

So i have 144 numbers, and all numbers beneath 1.000.000 needs to be multiplied by 2. Maybe 30 of these values are beneath 1.000.000...

How do i do this? Hope someone knows this

This is the code:

Data = readtable('Rejstrup Pyra .xlsx'); %Celcius

T_Pyra = table2array(Data(83:(223),8))

Radiation = table2array(Data(83:(223),3)) %kW/m^2

PV_radiation = Radiation./1000

T_modul = (T_Pyra)+(PV_radiation/20) %Celcius

T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100)

I_korrektion = 0.988

P_peak = 23947000 %watt

P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation %Watt

^^^^^^^^

This is my values for my power, where every value beneath 1.000.000 needs to be multiplied with 2.

Exporting it to excel (not relevant):

table_name=table(P_out1)

filnavn='Beregnet P_available fra Rejstrup.xlsx'

overskrift='P_available'

writetable(table_name,filnavn,'Sheet',overskrift)

Best regards

Peter

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Answer 1

Mathieu NOE 2022-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/1677489-multiply-array-if-number-is-under-certain-value#answer_923914

在 MATLAB Online 中打开

hello

this is very simple - see below :

P_out = 1000000 + 80000*randn(10,1); % dummy data
plot(P_out)
hold on
ind = P_out<=1000000; % find values below 1000000
P_out(ind) = P_out(ind)*2; % correction (put the right correction factor here)
plot(P_out,'-*')
hold off

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Peter Lyngbye 2022-3-22

This is the full code after adding yours:

Data = readtable('Rejstrup Pyra .xlsx'); %Celcius

T_Pyra = table2array(Data(87:(222),8));

Radiation = table2array(Data(87:(222),3)); %kW/m^2

PV_radiation = Radiation./1000;

T_modul = (T_Pyra)+(PV_radiation/20); %Celcius

T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100);

I_korrektion = 0.988;

P_peak = 23947000; %watt

P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt

P_out = 1000000 + 80000*randn(10,1); % dummy data

plot(P_out)

hold on

ind = P_out<=1000000; % find values below 1000000

P_out(ind) = P_out(ind)*2; % correction (put the right correction factor here)

plot(P_out,'-*')

hold off

The script is supposed to add temperature and iradiation from a solar park, and via formulas give the power collected from them which is P_out. But becuase of shadows in the park at early ours i need to multiply these values with a correction factor. The data from the excel have 5 minute logs of the radiation and temperature, which i will run through the script and compare to actual pwer readings from the park. I have added one of the excels for iradtioan and temp... I just noticed that actually telling matlab to multiply the early hours instedet of values beneath 1.000.000 would be more correct. I hope u understand what im asking, but a script multiplying for example the readings between 6:30 and 9:30 would be absolutely perfect! it is 24 hour clock

Best regards!

Mathieu NOE 2022-3-22

在 MATLAB Online 中打开

I was just finishing to modify your code for the correction in amplitude (x2 befoe 9:30 AM)

this is the code (a bit improved) and the result

but this is not what your last picture is telling me . It's a different correction method

so far the code is as pr your initial request

Data = readtable('Rejstrup Pyra .xlsx'); %Celcius
ind_start = 87;
ind_stop = 222;
Data = Data(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_time = datetime(Data.GeneratedOn);
T_Pyra = table2array(Data(:,8));
Radiation = table2array(Data(:,3)); %kW/m^2
PV_radiation = Radiation./1000;
T_modul = (T_Pyra)+(PV_radiation/20); %Celcius
T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100); 
I_korrektion = 0.988;
P_peak = 23947000; %watt
P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt
plot(Data_time,P_out)
hold on
ind = 116 - ind_start; % find time line corresponding 9:30 AM
P_out(1:ind) = P_out(1:ind)*2; % correction (put the right correction factor here)
plot(Data_time,P_out,'-*')
legend('before correction','after correction');
hold off

Mathieu NOE 2022-3-22

在 MATLAB Online 中打开

Sorry but the correction you want is not a factor 2. it much less than that (and it varies with the time value) but I cannot guess it because the grey reference line is not supplied in your data ...

also I don't understand why the blue should match the grey curve simply for the appearance , you are introducing a bias on purpose in your code just to make things look better ??

In the mean time I fixed the previous problem (Unrecognized table variable name 'GeneratedOn'.)

Data = readtable('Rejstrup Pyra .xlsx','VariableNamingRule' ,'preserve'); %Celcius
ind_start = 87-40;
ind_stop = 222;
Data = Data(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_time = datetime(table2array(Data(:,1)));
T_Pyra = table2array(Data(:,8));
Radiation = table2array(Data(:,3)); %kW/m^2
PV_radiation = Radiation./1000;
T_modul = (T_Pyra)+(PV_radiation/20); %Celcius
T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100); 
I_korrektion = 0.988;
P_peak = 23947000; %watt
P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt
plot(Data_time,P_out)

Mathieu NOE 2022-3-22

在 MATLAB Online 中打开

okay

it's my turn to become nuts ... :) I still don't get what you want to correct from the P_out generated by the matlab code.

The top plot is your curves , the bottom one is the full 24 hours of P_out as it comes without any further corrections beside what you have already coded

so what correction in the lower plot do you want to do ? that is still unclear to me - make a handheld sketch if you want.

code used for the lower plot :

clc
clearvars
Data = readtable('Rejstrup Pyra .xlsx','VariableNamingRule' ,'preserve'); %Celcius
[m,n] = size(Data);
ind_start = 1;  % 87-40
ind_stop = m;  % 222
Data = Data(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_time = datetime(table2array(Data(:,1)));
T_Pyra = table2array(Data(:,8));
Radiation = table2array(Data(:,3)); %kW/m^2
PV_radiation = Radiation./1000;
T_modul = (T_Pyra)+(PV_radiation/20); %Celcius
T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100); 
I_korrektion = 0.988;
P_peak = 23947000; %watt
P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt
plot(Data_time,P_out)

Mathieu NOE 2022-3-22

在 MATLAB Online 中打开

ok

this is where you should have started first

I took your last excel file (I removed the columns above B to speed up the code) into consideration

now I can draw the two lines (and understand the purpose of the code)

you can do all modifications you want up to force the blue to match the grey (simply compute the amplitude ratio at each time interval... or build a strategy around that)

so far it seems now you have reached your target...

clc
clearvars
%% reference data (grey)
Data_ref = readtable('Rejstrup Effekt.xlsx','VariableNamingRule' ,'preserve'); %Celcius
[m,n] = size(Data_ref);
ind_start = 60;  % 
ind_stop = 222;  % 
Data_ref = Data_ref(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_ref_time = datetime(table2array(Data_ref(:,1)));
P_out_ref= table2array(Data_ref(:,2));
plot(Data_ref_time,P_out_ref)
%% measurement (blue, to be corrected)
Data = readtable('Rejstrup Pyra .xlsx','VariableNamingRule' ,'preserve'); %Celcius
[m,n] = size(Data);
Data = Data(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_time = datetime(table2array(Data(:,1)));
T_Pyra = table2array(Data(:,8));
Radiation = table2array(Data(:,3)); %kW/m^2
PV_radiation = Radiation./1000;
T_modul = (T_Pyra)+(PV_radiation/20); %Celcius
T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100); 
I_korrektion = 0.988;
P_peak = 23947000; %watt
P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt
% heavy correction : make the blue match exactly the grey
cor_factor = P_out_ref./(P_out+eps); % + eps to avoid division by zero !
P_out_corrected = P_out.*cor_factor;
plot(Data_ref_time,P_out_ref,'k',Data_time,P_out,'b',Data_time,P_out_corrected,'c*')
legend('ref (grey)','blue (uncorrected)','blue (100% corrected)');

Peter Lyngbye 2022-3-22

This is perfect!

Only last thing i need is this adjustment but for the other half of the curve (late hours):

ind = 130 - ind_start; % find time line corresponding 9:30 AM

P_out(1:ind) = P_out(1:ind)*0.97; % correction (put the right correction factor here)

Right now it only adjust the early hours :/

Mathieu NOE 2022-3-22

在 MATLAB Online 中打开

ok

I put back those lines in the code (see below) , but I have a hard time to see what the 0.97 makes as an improvement ?? or did I forgot another piece of code from the past ?

this is not doing any shift in the early hours...

see figure 1 (below)

figure 2 is simply the "heavy" correction method I already posted above

clc
clearvars
%% reference data (grey)
Data_ref = readtable('Rejstrup Effekt.xlsx','VariableNamingRule' ,'preserve'); %Celcius
% [m,n] = size(Data_ref);
ind_start = 60;  % 
ind_stop = 222;  % 
Data_ref = Data_ref(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_ref_time = datetime(table2array(Data_ref(:,1)));
P_out_ref= table2array(Data_ref(:,2));
plot(Data_ref_time,P_out_ref)
%% measurement (blue, to be corrected)
Data = readtable('Rejstrup Pyra .xlsx','VariableNamingRule' ,'preserve'); %Celcius
% [m,n] = size(Data);
Data = Data(ind_start:ind_stop,:); % retrict all table data between two time indexes from 7:10 AM to 18:25 PM
Data_time = datetime(table2array(Data(:,1)));
T_Pyra = table2array(Data(:,8));
Radiation = table2array(Data(:,3)); %kW/m^2
PV_radiation = Radiation./1000;
T_modul = (T_Pyra)+(PV_radiation/20); %Celcius
T_korrektion = 1-(T_modul-T_Pyra).*(0.40/100); 
I_korrektion = 0.988;
P_peak = 23947000; %watt
P_out = P_peak.*T_korrektion.*I_korrektion.*PV_radiation; %Watt
%% basic correction
P_out_corrected = P_out; % init P_out_corrected
ind = 116 - ind_start; % find time line corresponding 9:30 AM
Data_ref_time(ind)
P_out_corrected(1:ind) = P_out_corrected(1:ind)*0.97; % correction # 1  (put the right correction factor here)
figure(1),
plot(Data_ref_time,P_out_ref,'k',Data_time,P_out,'b',Data_time,P_out_corrected,'c*')
legend('ref (grey)','blue (uncorrected)','blue (corrected)');
%% full correction (remove code below if necessary)
% make the blue match exactly the grey
P_out_corrected = P_out; % init P_out_corrected
ind = P_out<eps;
P_out_ref(ind) = 0; % avoid very high (inf) cor_factor due to division by eps !
cor_factor = P_out_ref./(P_out+eps); % + eps to avoid division by zero if P_out = 0 !
P_out_corrected = P_out_corrected.*cor_factor;
figure(2),
plot(Data_ref_time,P_out_ref,'k',Data_time,P_out,'b',Data_time,P_out_corrected,'c*')
legend('ref (grey)','blue (uncorrected)','blue (corrected)');

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Multiply array if number is under certain value

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Multiply array if number is under certain value

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