Read and write multiple times in excel document - for loop or?

Hi,

I am using polyfit to fit the dataset I have.

function Polyfit_data(x_colomn,y_colomn,cell_with_power_value)
x1=xlsread('data.xlsx','data',x_colomn); %'x' data from simulation or measurement
y1=xlsread('data.xlsx','data',y_colomn); %'y' data from simulation or measurement
power=xlsread('data.xlsx','data',cell_with_power_value); %power dissipated in device
p=polyfit(x1,y1,20);
xlswrite('polyfitdata.xlsx',p,'b1:bb1');
xlswrite('polyfitdata.xlsx',power,'a1:a1');

my data I have sorted so that the first dataset have x's in a:a, y's in b:b and power=c1, next dataset then have x's in d:d, y's in e:e and power=f1 ... This continiues for multiple dataset.

Each data set is read and then a polyfit function is found and written in another excel document. Here I write the polynomia from b1:bb1 and power value in a1.

First I am not sure if I should write it back to an excel file - since when I am using the data later I have to read them and it takes quiet some time. Second I would really like to make the function as a loop where I only define how many dataset to read. Then I just need to be careful that the data is organized in the right way.

The script I am using later is simply reading the polyfit functions, linearise for power input and then adding the plots together to give a sum.

t_end=xlsread('polyfitdata.xlsx','parameters','b5:b5');
stepsize=xlsread('polyfitdata.xlsx','parameters','b6:b6');
Ta=xlsread('polyfitdata.xlsx','parameters','b7:b7');
x0=0:stepsize:t_end;
%die1 settings
t_0_die1=xlsread('polyfitdata.xlsx','parameters','b2:b2');
pow11=xlsread('polyfitdata.xlsx','polyfitdata','b2:b2');
pow14=xlsread('polyfitdata.xlsx','polyfitdata','b3:b3');
power1=xlsread('polyfitdata.xlsx','parameters','b3:b3');
p11=xlsread('polyfitdata.xlsx','polyfitdata','c2:w2');
p14=xlsread('polyfitdata.xlsx','polyfitdata','c3:w3');
%die2 settings
t_0_die2=xlsread('polyfitdata.xlsx','parameters','c2:c2');
pow21=xlsread('polyfitdata.xlsx','polyfitdata','b4:b4');
pow24=xlsread('polyfitdata.xlsx','polyfitdata','b5:b5');
power2=xlsread('polyfitdata.xlsx','parameters','c3:c3');
p21=xlsread('polyfitdata.xlsx','polyfitdata','c4:w4');
p22=xlsread('polyfitdata.xlsx','polyfitdata','c5:w5');
%die3 settings
t_0_die3=xlsread('polyfitdata.xlsx','parameters','d2:d2');
pow31=xlsread('polyfitdata.xlsx','polyfitdata','b6:b6');
pow34=xlsread('polyfitdata.xlsx','polyfitdata','b7:b7');
power3=xlsread('polyfitdata.xlsx','parameters','d3:d3');
p31=xlsread('polyfitdata.xlsx','polyfitdata','c6:w6');
p32=xlsread('polyfitdata.xlsx','polyfitdata','c7:w7');
%die1
x1=0:stepsize:t_end-t_0_die1;
y1=[zeros(1,size(x0,2)-size(x1,2)),(polyval(p14,x1)-polyval(p11,x1))/(pow14-pow11)*power1];
%die2
x2=0:stepsize:t_end-t_0_die2;
y2=[zeros(1,size(x0,2)-size(x2,2)),(polyval(p22,x2)-polyval(p21,x2))/(pow24-pow21)*power2];
%die3
x3=0:stepsize:t_end-t_0_die3;
y3=[zeros(1,size(x0,2)-size(x3,2)),(polyval(p32,x3)-polyval(p31,x3))/(pow34-pow31)*power3];
%Creating total sum vector
y_total=y1+y2+y3+Ta*ones(1,size(x0,2)); % Sum of curves from die1, die2 and die3
%plot
plot(x0,y_total)

Answer 1

[Titus Edelhofer]

Hi Jakob,

xlsread in the background opens Excel, reads the data and closes it. This takes some time, therefore I would suggest to read the data not one by one, but as one large block. Within your MATLAB code you then read portions (even in a loop, if you like). This should make everything easier and faster.

Titus

[Stephen23]

Jakob's "Answer" moved here:

That I will try to do. Simple just read one time the qhole sheet and then read out inside matlab afterwards.