problem to plot graph

I am try to plot graph from excel file using matlab.it is 2 column and 1000 row file. I got problem and don't know how to solve this problem.

My codes are

a = xlsread('frequencyresponse_cone2.xlsx');

U = a(:,2);

mag = 20*log10(abs(U));

f = a(:,1);

semilogx(f,mag);

grid;

title('Voltage Divider')

xlabel('Frequency [Hz]')

ylabel('Magnitude [dB]')

sys=frd(abs(U),f);

bd=bandwidth(sys)

I have got this following error

Attempted to access a(:,2); index out of bounds because size(a)=[1000,1].

Error in ploting_bandwidth_plex_shield (line 4)

U = a(:,2);

I can not understand the problem. I put some of my data from file.

100          0.012306987852045518+9.955546191163225E-9i
1001100.901  0.012308491603736954+9.963642914141967E-5i
2002101.802  0.012312995435215674+1.9909141167179524E-4i
3003102.703  0.012320478963642677+2.9820480108037103E-4i
4004103.604  0.012330908495129297+3.9680921522587394E-4i
5005104.505  0.012344237432945524+4.947412933337127E-4i
6006105.405  0.012360406835903089+5.918429292528212E-4i
7007106.306  0.01237934611438875+6.879624169109924E-4i
8008107.207  0.01240097384873408+7.829554908591458E-4i
9009108.108  0.012425198712354842+8.766862477062554E-4i
101             0.012306987852045518+9.955546191163225E-9i

please help me solve this problem.

Answer 1

[Walter Roberson]

Microsoft Excel does not support complex numbers by default. You need to enable the Analysis Toolpak in order to create complex numbers -- without that, anything you enter in complex form is just considered to be a text string.

I see that writetable() from MATLAB drops complex components as it writes, so it is not possible to just use the work-around of writetable() to get complex data into a form that can be read back.

I happen to be using Excel for Mac 2011. It turns out that the Analysis add-on is not available for that; they refer me to the third-party xlstat package, which would be a minimum of $US295 dollars per year (I do not qualify as academic.) And that is minimum -- there are premium add-ons and it is not clear which of those would be needed to support complex numbers.

I would suggest to you that you simply make the complex component a third column in the xlsx file, and put the two columns back together again after reading in the data, by using

U = complex(a(:,2),a(:,3))