I get it what you are trying to achieve. Here is the code I developed after a little modification of yours.
clear all;
clc;
[fid, msg] = fopen('hw12_2.txt','r');
if fid==-1
fprintf(2,'FAILED TO OPEN FILE. %s\n', msg);
return;
end
% FIRST LINE OF DATA
title_str= fgetl(fid);
% Initialize z and y axis arrays
xstr =[];
ystr =[];
aline = 1;
while aline ~= -1
% SECOND LINE HAS LABELS
aline=fgetl(fid);
if (aline ~= -1)
[x_str, y_str_temp] = strtok(aline);
[Dec, y_str] = strtok(y_str_temp);
x_str = str2double(x_str);
y_str = str2double(y_str);
% cmpr stores the result of comparison of both strings i.e. check
% whether it is equal to BC or not
cmpr = strcmp(Dec, 'BC');
if (cmpr == 1)
x_str = -1 * x_str;
end
xstr = [xstr x_str];
ystr = [ystr y_str];
end
end
% Convert the y-axis in log scale
ystr = log10(ystr);
bar(xstr,ystr);
% USE LABELS FROM ABOVE USING FIRST AND SECOND LINE
xlabel('Year');
ylabel('Population');
title(title_str);
It works perfectly fine and just like the way you want it, but you have to take care of one thing that the text file must not have any empty lines between the line with actual text, otherwise the compiler would take that the file has ended and it will return a -1. It should be like this
YEAR BC/AD POPULATION
10000 BC 1000000
8000 BC 5000000
6500 BC 5000000
5000 BC 5000000
This way it will work absolutely fine. Hope it helps
