MATLAB: How to plot data in block

data in block

   Hello, I've data in .txt file as follows:
   -42.135   -40.263   -38.384   -36.498   -34.608   -32.712   -30.811   -28.907   -26.999   -25.088
   -23.174   -21.258   -19.339   -17.419   -15.497   -13.573   -11.648    -9.723    -7.796    -5.868
    -3.940    -2.012    -0.084     1.845     3.773     5.701     7.629     9.555    11.481    13.406
    15.330    17.252    19.173    21.092    23.008    24.922    26.833    28.742    30.646    32.547
    34.443    36.335    38.220    40.100    41.972    43.837    45.692    47.537    49.371    51.191
    52.995    54.781 
     5.543     5.325     5.061     4.786     4.535     4.328     4.146     3.988     3.864     3.779
     3.728     3.705     3.715     3.763     3.862     4.044     4.375     4.985     6.032     7.594
     9.759    12.214    13.494    14.008    13.810    13.130    12.751    12.998    13.764    14.557
    14.307    13.415    13.135    13.130    12.965    12.590    11.975    11.391    10.867    10.446
    10.088     9.760     9.401     9.021     8.594     8.124     7.615     7.106     6.737     6.495
     6.292     6.119
I want to plot above upper block(52 data points) data in x-axis and that in lower block in y-axis using matlab command. Any suggestions?

Best Answer

Knowing the length of the data sections makes it pretty easy even though they're not regular in the file--
fid=fopen('yourfile.txt','r');  % open the data file to read...
x=fscanf(fid,'%f',52);          % read the known number of x values
y=fscanf(fid,'%f',52);          % followed by y values
fid=fclose(fid);
plot(x,y)
NB: that fscanf will
  1. Read the first N requested values (and no more) into 'x', and then
  2. skip the blanks in the file to read the 52 more values into 'y'
Since that works like magic, afterwards the plotting is trivial. If use importdata or one of the other higher-level routines, it would read all the data but then you've got a mess in trying to sort out "who's who in the zoo" as those routines will return a regular array w/ NaN for the missing values in the rows shorter than the rest.
Related Question