I have an error that im not sure how to fix

My code is producing the error of matrix dimensions must agree. Im not sure how to fix it. Can anyone help me?

clear % clears assigned values from memory
clc % clears command window

m = [0.15 0.14 0.13 0.12 0.11 0.1 0.09 0.08 0.07 0.06 0.05];
% constant mass used for all of the spring trials, measued in kg.
L1 = [0.63 0.65 0.605 0.58 0.54 0.49 0.47 0.43 0.395 0.36 0.32];
% lengths obtained from the 1st long spring trial, measured in meters.
L2 = [0.62 0.63 0.54 0.51 0.42 0.41 0.39 0.38 0.36 0.32 0.28];
% lengths obtained from the 2nd long spring tiral, measured in meters.
L3 = [0.18 0.17 0.16 0.15 0.12 0.122 0.11 0.1 0.1 0.09 0.09];
% lengths obtained from shorter spring trial, measured in meters.
L_01 = (0.15);
% relaxed length of the 1st long spring, measured in meters.
L_02 = (0.12);
% relaxed length of the 2nd long spring, measured in meters. 
L_03 = (0.095);
% relaxed length of the short spring, measured in meters.
g = 9.8;
% gravitational constant, measured in meters per second^2

%Model Equations
x1 = ((1) ./ (m.*g));
y1 = ((1) ./ (L1) - (L_01));

x2 = ((1) ./ (m.*g));
y2 = ((1) ./ (L2 - L_02));

x3 = ((1) ./ (m.*g));
y3 = (11) ./ (L3) - (L_03);

%Sets up G matrix
G1=x1;
G1 = ones(length(x1),1);
G1(:,2)=x1;

G2=x2;
G2 = ones(length(x2),1);
G2(:,2)=x2;

G3 = x3;
G3 = ones(length(x3),1);

%spring constants
k1=G1\y1;
k2=G2\y2;
k3=G3\y3;

%creates line
X1 = [min(x1): 1e-3: max(x1)]';
X2 = [min(x2): 1e-3: max(x2)]';
X3 = [min(x3): 1e-3: max(x3)]';

Y1 = k1 (1,1)+k1(2,1).*X1;
Y2 = k2 (1,1)+k2(2,1).*X2;
Y3 = k3 (1,1)+k2(2,1).*X3;

%Uncertainties
sig1 = sqrt(sum((y1-G1*k1).^2/(length(x1)-1)));
sig2 = sqrt(sum((y2-G2*k2).^2/(length(x2)-1)));
sig3 = sqrt(sum((y3-G3*k3).^2/(length(x3)-1)));

se1_1 = sig1.*sqrt(1./((length(x1)+(X1)-mean(x1)^2)/((length(x1)-1)*std(x1)^2))); % error for k1
se1_2 = sig2.*sqrt(1./((length(x_2)+mean(x_2)^2)/((length(x_2)-1)*std(x_2)^2))); % error for k1


se2_1 = sig1.*sqrt(1./((length(x1)-1)*std(x1)^2)); % error for k2
se2_2 = sig2.*sqrt(1./((length(x2)-1)*std(x2)^2)); % error for k2

%ci1 = tinv(0.975, length(x1)-2).*se11;
%ci2 = tinv(0.975, length(x2)-2).*se12;

SE1 = sig1.*sqrt(1/length(x1) + (X1 - mean(x1)).^2/((length(x1) - 1)*std(x1).^2));
SE2 = sig2.*sqrt(1/length(x2) + (X2 - mean(x2)).^2/((length(x2) - 1)*std(x2).^2));
SE3 = sig3.*sqrt(1/length(x3) + (X3 - mean(x3)).^2/((length(x3) - 1)*std(x3).^2));

CI1 = tinv(0.975, length(x1) - 1).*SE1;
CI2 = tinv(0.975, length(x2) - 1).*SE2;
CI3 = tinv(0.975, length(x3) - 1).*SE3;

figure(1) %this is a certain type of figure Matlab will draw
clf %clears existing graphs
plot(x1,y1,'ob') %plot command
%plots solid blue circles of size "5"
hold on %Prompt to matlab that more things will be added(?)
plot(X1,Y1, 'r-', 'LineWidth', 2) 
plot(X1,Y1+CI1, 'g--', 'LineWidth', 1)
plot(X1,Y1-CI1, 'g--', 'LineWidth', 1)
hold off %Finished plotting
xlabel('$$\frac{1} {mg} $$ ','Interpreter','Latex')
ylabel('$$\frac{1} {l_1-l_0}$$ ','Interpreter','Latex')
print(figure(1),'-dpng', 'lab4fig1') %displays graph
% set(figure(1),'color','white')

figure(2) %this is a certain type of figure Matlab will draw
clf %clears existing graphs
plot(x2,y2,'ob') %plot command
%plots solid blue circles of size "5"
hold on %Prompt to matlab that more things will be added
plot(X2, Y2, 'r-', 'LineWidth', 2) 
plot(X2, (Y2+CI2), 'g--', 'LineWidth', 1)
plot(X2, (Y2-CI2), 'g--', 'LineWidth', 1)
hold off %Finished plotting
xlabel('$$\frac{1} {mg} $$ ','Interpreter','Latex')
ylabel('$$\frac{1} {l_1-l_0}$$ ','Interpreter','Latex')
print(figure(2),'-dpng', 'lab4fig2') %displays graph
% set(figure(2),'color','white')

figure(3) %this is a certain type of figure Matlab will draw
clf %clears existing graphs
plot(x3,y3,'ob') %plot command
%plots solid blue circles of size "5"
hold on %Prompt to matlab that more things will be added
plot(X3, Y3, 'r-', 'LineWidth', 2) 
plot(X3, (Y3+CI2), 'g--', 'LineWidth', 1)
plot(X3, (Y3-CI2), 'g--', 'LineWidth', 1)
hold off %Finished plotting
xlabel('$$\frac{1} {mg} $$ ','Interpreter','Latex')
ylabel('$$\frac{1} {l_1-l_0}$$ ','Interpreter','Latex')
print(figure(3),'-dpng', 'lab4fig3') %displays graph
% set(figure(3),'color','white')

Answer 1

[Walter Roberson]

k1=G1\y1.';

probably.