How to get multiple slopes from a file.

I have files, where the first column represent as x axis and the other columns are for y axis. I can get different XY curves by plotting them. For example, by plotting the first column with the second column I get one graph, again by plotting the first column with the third column I get another curve and so on. I need to calculated the slopes of each curves. Until now I have the programming to calculate the slop for one curve and to get all of the slopes together, I have to change some values again and again, but I prefer to do it manually and save them as a csv file. Can any one help me with this? I am totally new at matlab, any kind of help would be appreciated.

reading = csvread("test.csv");
x = reading(:,1);
y = reading (:,7);
x1q = find((x >= -0.6) & (x <=-0.45))% range -0.6 and -0.45
    p=polyfit(x(x1q), y(x1q),1)
    slope= p(1)
figure(2)
plot(x, y, '-b')
 hold on
 plot(x(x1q), y(x1q),'ok');

Answer 1

[KSSV]

You have to run a loop for each column for which you want to get slopes.

data = csvread("test.csv");
[m,n] = size(data) ; 
slope = zeros(n-1,1) ; 
x = data(:,1);
for i = 2:n
    y = data (:,i);   % pick each column 
    idx = find((x >= -0.6) & (x <=-0.45))% range -0.6 and -0.45
    p=polyfit(x(idx), y(idx),1) ; 
    slope(i-1) = p(1)
end

[Minions]

Thank you so much for the help. It really worked. But i have one question, after running the slope I got the results for 10 colums, where I have 9 colums in y axis, so I should get 9 results for slope right?

[KSSV]

yes...you have nine data points (x,yi); i = 1:9..so you end up with 9 slopes.

[Minions]

hmm, but i ended up with 10 slopes, and one of them only have one and 0.

[KSSV]

Yes you are right......edited the code...loop should be from 2 to n....

[Minions]

ok, thank you so much for the help.