Index Error when plotting - was working now not!

I am coding for a project and the figure 1 plot was working fine and then all the sudden it keep giving me:

"Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in Lab1_Light_scattering_and_absorption (line 34)

plot(x_h2o, y_h2o, x_milk_front, y_milk_front, x_milk_side, y_milk_side);"

when I didn't chnage anything so I am confused.

This is the code:

h2o_light = load("Lab1_Milk_Scattering_USB2E57541_15-07-20-121.txt"); % Light Source + Water

x_h2o = h2o_light(:,1);

y_h2o_light = h2o_light(:,2);

h2o_dark = load("Lab1_Milk_Scattering_USB2E57541_15-08-22-949.txt"); % Dark Background

y_h2o_dark = h2o_dark(:,2);

% Corrected Spectra: Subtract Background

y_h2o = y_h2o_light - y_h2o_dark;

milk_front_light = load("Lab1_Milk_Scattering_USB2E57541_15-19-35-431.txt"); % Milk Front

x_milk_front = milk_front_light(:,1);

y_milk_front_light = milk_front_light(:,2);

milk_front_dark = load("Lab1_Milk_Scattering_USB2E57541_15-20-08-946.txt"); % Dark Background

y_milk_front_dark = milk_front_dark(:,2);

% Corrected Spectra: Subtract Background

y_milk_front = y_milk_front_light - y_milk_front_dark;

milk_side_light = load("Lab1_Milk_Scattering_USB2E57541_15-39-12-053.txt"); % Milk Side

x_milk_side = milk_side_light(:,1);

y_milk_side_light = milk_side_light(:,2);

milk_side_dark = load("Lab1_Milk_Scattering_USB2E57541_15-43-36-313.txt"); % Dark Background

y_milk_side_dark = milk_side_dark(:,2);

% Corrected Spectra: Subtract Background

y_milk_side = y_milk_side_light - y_milk_side_dark;

% Plot with 3 spectra overlaid

plot(x_h2o, y_h2o, x_milk_front, y_milk_front, x_milk_side, y_milk_side);

legend('Water Spectra', 'Milk Forward Spectra', 'Milk Side Spectra');

xlabel('Wavelength (nm)');

ylabel('Absorbance');

title('Light Scattering');

h2o_light2 = load("Lab1_Milk_Scattering_USB2E57541_15-54-13-352.txt"); % Light Source + Water

x_h2o2 = h2o_light2(:,1);

y_h2o2 = h2o_light2(:,2);

h2o_dark2 = load("Lab1_Milk_Scattering_USB2E57541_15-55-27-324.txt"); % Dark Background

y_h2o_dark2 = h2o_dark2(:,2);

% Corrected Spectra: Subtract Background

y_h2o2 = y_h2o2 - y_h2o_dark2;

PR_long = load("Lab1_Milk_Scattering_USB2E57541_15-59-06-383.txt"); % Phenol Red Long

x_PR_long = PR_long(:,1);

y_PR_long = PR_long(:,2);

PR_short = load("Lab1_Milk_Scattering_USB2E57541_16-03-54-358.txt"); % Phenol Red Short

x_PR_short = PR_short(:,1);

y_PR_short = PR_short(:,2);

PR1V = load("Lab1_Milk_Scattering_USB2E57541_16-21-44-291.txt"); % Phenol Red + 1 Drop Vinegar

x_PR1V = PR1V(:,1);

y_PR1V = PR1V(:,2);

PR2V = load("Lab1_Milk_Scattering_USB2E57541_16-26-13-561.txt"); % Phenol Red + 2 Drops Vinegar

x_PR2V = PR2V(:,1);

y_PR2V = PR2V(:,2);

PR3V = load("Lab1_Milk_Scattering_USB2E57541_16-29-59-054.txt"); % Phenol Red + 3 Drops Vinegar

x_PR3V = PR3V(:,1);

y_PR3V = PR3V(:,2);

PR1B = load("Lab1_Milk_Scattering_USB2E57541_16-37-15-766.txt"); % Phenol Red + 1 Drop Bleach

x_PR1B = PR1B(:,1);

y_PR1B = PR1B(:,2);

PR2B = load("Lab1_Milk_Scattering_USB2E57541_16-40-37-492.txt"); % Phenol Red + 2 Drops Bleach

x_PR2B = PR2B(:,1);

y_PR2B = PR2B(:,2);

PR3B = load("Lab1_Milk_Scattering_USB2E57541_16-43-36-069.txt"); % Phenol Red + 3 Drops Bleach

x_PR3B = PR3B(:,1);

y_PR3B = PR3B(:,2);

% Plot water spectra and Phenol Red spectra (long and short pathlengths, without vinegar/bleach) overlaid in the same figure

figure(2);

plot(x_h2o2, y_h2o2, x_PR_long, y_PR_long, x_PR_short, y_PR_short);

legend('Water Spectra', 'Long Phenol Red Specta', 'Short Phenol Red Spectra');

xlabel('Wavelength (nm)');

ylabel('Absorbance');

%plot(x_PR1V, y_PR1V, x_PR2V, y_PR2V, x_PR3V, y_PR3V, x_PR1B, y_PR1B, x_PR2B, y_PR2B, x_PR3B, y_PR3B);

% Plot absorption coefficent*pathlengths obtained for both long and short pathlengths overlaid in the same figure

P_in = y_h2o; % Light power entering the solution = spectrum measured through water

P_out_long = y_PR_long;

P_out_short = y_PR_short;

u_L_long = -log(P_out_long/P_in);

u_L_short = -log(P_out_short/P_in);

plot(x_h2o, y_h2o, x_PR_long, y_PR_long, x_PR_long, u_L_long, x_PR_short, y_PR_short, x_PR_short, u_L_short);

legend('Water Spectra', 'Long Phenol Red Specta', 'Absorbance Coefficient*Pathlength Through Long Phenol Red', 'Short Phenol Red Spectra', 'Absorbance Coefficient*Pathlength Through Short Phenol Red');

xlabel('Wavelength (nm)');

ylabel('Absorbance');

wo_RB = load("Lab1_Milk_Scattering_USB2E57541_16-51-04-898.txt"); % Without Rubber Band

x_wo_RB = wo_RB(:,1);

y_wo_RB = wo_RB(:,2);

w_RB1 = load("Lab1_Milk_Scattering_USB2E57541_16-54-33-159.txt"); %

x_w_RB1 = w_RB1(:,1);

y_w_RB1 = w_RB1(:,2);

w_RB2 = load("Lab1_Milk_Scattering_USB2E57541_16-54-53-603.txt"); %

x_w_RB2 = w_RB2(:,1);

y_w_RB2 = w_RB2(:,2);

% Produce plots of the spectra overlaid in the same figure

plot(x_wo_RB, y_wo_RB, x_w_RB1, y_w_RB1, x_w_RB2, y_w_RB2);

Answer 1

[Cris LaPierre]

Clear your workspace and then rerun your code.

This error suggests you have created a variable named plot, which is taking precedence over MATLAB's plot function. Removing that variable from your workspace should fix the error.

[Elizabeth Avery]

OMG BLESS! THANK YOU