How to plot a single column of values with a linear regression line through it

I have a column that I wann plot and have a regression line go through it, How would I do that?

my code so far is:

figure(1)

title('Phase1')

plot(FG)

[darova]

What about polyfit?

[isamh]

thanks for the reply, I tried two different ways and both didnt seem to work. Would it be possible to do the regression line for just one column? I know we can plot one column like this: plot(X) and plost the columns values against number of rows. I know i didnt do that for the code i listed but how would i do both?

1)

figure(1)

X = Fengd_1;

Y = WATT_HR_1;

plot(X,Y,'.b')

p = polyfit(X,Y,1);

f = polyval(p,X);

hold on

plot(X,f,'--r')

2)

figure(1)

X = Fengd_1;

Y = WATT_HR_1;

format long

B1 = X\Y;

YCalc1 = B1*X;

scatter(X,Y)

hold on

plot(X,YCalc1)

title('Phase1')

grid on

[Image Analyst]

Attach X and Y in a mat file so we can show you.

save('answers.mat', 'X', 'Y');

In the meantime, see my attached polyfit() demo.

[darova]

• I added the: save('answers.mat', 'X', 'Y'); to both codes and still didnt the regression line.

Image Analyst can you cooperate?

[isamh]

Lol I just noticed what was wrong with that. Thought he wanted me to do something else, I’m unable to provide the data now and was wondering if we could just use random data. Forgot to mention that i have some NAN rows with both columns, would that effect the results?

Answer 1

[darova]

Here is a simple example (i made it special for you)

N = 20;
x = linspace(0,3,N);
y = 2*x + rand(1,N);
p = polyfit(x,y,1);
y1 = polyval(p,x);
plot(x,y,'.r')
hold on
plot(x,y1,'b')
hold off

• Forgot to mention that i have some NAN rows with both columns, would that effect the results?

Then you should do interpolation without NaN

ix = ~isnan(y);             % choose indices that are not NaN
x1 = x(ix);
y1 = y(ix);
p = polyfit(x1,y1,1);
y2 = polyval(p,x1);

[isamh]

Trued that but I believe the columns are now unequal lengths. I get this error message: error with p1=polyfit(X1,Y1,1);

[darova]

Please post the entire error and code you used