Plotting certain columns from a .dat file

Greetings all,

It's been quite some time since I've used MATLAB, and embarrasingly I've been struggling with this all day. Needless to say I am a bit rusty! I have a data file that has 8 columns of data (and has headers at the top). Right now I'm trying to just plot column 2 of the data on the x-axis and plot the 4th and 8th columns as two line plots along the y-axis.

   I imagine you use fopen and textscan, but there's so many to choose from. Maybe importdata?

    Any help would be appreciated. Thanks!

Answer 1

[Fangjun Jiang]

If your data file format is consistent, try

data=importdata('MyFile.data');

For plotting, if you have a matrix A, A(:,2) is all the data in the second column so you can do:

plot(A(:,2),A(:,4),'r',A(:,2),A(:,8),'b');

[Jesse]

Fangjun, ok thanks, but how would you go about plotting certain columns of the file as stated in the above question?

[Jesse]

Fangjun, ok thanks, but how would you go about plotting certain columns of the file as stated in the above question?

[Fangjun Jiang]

See update.

[Jesse]

Fangjun, thanks again. However, I did what you said:

data = importdata('MyFile.dat');

plot(data(:,2),data(:,4),'r',data(:,2),data(:,8),'b');

But I receive

??? Index exceeds matrix dimensions.

Error in ==> Tester2 at 5

plot(data(:,2),data(:,4),'r',data(:,2),data(:,8),'b');

data is somehow a 1x1 struct, not a matrix. Should I try another function?

[Fangjun Jiang]

data is a structure, type data in Command Window to see what it contains. You need to do A=data.data.

You've used MATLAB long time ago so maybe going through the "Getting Started" in MATLAB document is beneficial.

[Jesse]

Fangjun,

Ah yes! I forgot about the . operator to make the matrices agree!

Thanks - that worked!