Code to combine ROC curves and tell which one is better

Hi,

I want to make a ROC curve combining the ROC graphs from all the three sheets in the attached excel file into a single ROC curve, comparing the curves to determine which one is better. Below mentioned is the code that I am using to make a ROC curve from one sheet on this excel file. What changes should I make to the following code so that it gives me a ROC curve for all the three sheets in one plot?

>>meanthresh = 0.8:0.1:2.5; % This alters the mean threshold between 0.8 and 2.5 by 0.1

rocTable = readtable('ROC.xlsx','range','$A1:$D17');

%% Beginning the Mean ROC

for a = 1:length(meanthresh) %% the for loop makes it to where the threshold is automatically altered and you do not have to do it manually

positive_a = meanthresh(a) < (rocTable.Average); % declaring an algorithm to determine if the value is greater than the threshold

true = rocTable.FID == 1; %true = if the data in the column is equal to (==) 1

false = rocTable.FID == 0; %false = if the data in the column is equal to (==) 0

TP = sum(positive_a(true)); %true positive = if both the true statement (true) and the positive statement (positive_a) are met, then sum all the true values

FP = sum(positive_a(false)); %false positive = if both the false statement (false) and the positive statement (positive_a) are met, then sum all the false values

FN = sum(true) - TP; %false negative = sum of all true values minus the true positives

TN = sum(false) - FP; %true negative = sum of all false values minus the false positives

sensitivity_a(a) = (TP/(TP+FN)); %%sensitivity equation

specificity_a(a) = (TN/(TN+FP)); %%specificity equation

end %% end of for loop

stdevthresh = 0:0.1:1.7; %This alters the stdev threshold from 0 to 1.7 by 0.1

% Beginning of St Dev ROC

for b = 1:length(stdevthresh)

positive_b = stdevthresh(b) < (rocTable.SD); % declaring an algorithm to determine if the value is greater than the threshold

true = rocTable.FID == 1; %true = if the data in the column is equal to (==) 1

false = rocTable.FID == 0; %false = if the data in the column is equal to (==) 0

TPsd = sum(positive_b(true)); %true positive = if both the true statement (true) and the positive statement (positive_b) are met, then sum all the true values

FPsd = sum(positive_b(false)); %false positive = if both the false statement (false) and the positive statement (positive_b) are met, then sum all the false values

FNsd = sum(true) - TPsd; %false negative = sum of all true values minus the true positives

TNsd = sum(false) - FPsd; %true negative = sum of all false values minus the false positives

sensitivity_b(b) = (TPsd/(TPsd+FNsd)); %%equations for sensitivity and specificity

specificity_b(b) = (TNsd/(TNsd+FPsd));

end

plot(1-specificity_b, sensitivity_b, 'Marker', '.', 'MarkerSize', 16, 'LineWidth', 1); %%this is the standard deviation plot

hold on %%allows more than one graph to be on the same plot--must be followed by "hold off" when done

plot(1-specificity_a, sensitivity_a, 'Marker', '.', 'MarkerSize', 24, 'LineWidth', 1); %%plotting command for the mean ROC

hold off

legend('St. Devs', 'Averages'); %%this puts a legend on the graph--legend('first name', 'second name')

xlabel('False Positive Rate'); %%label on x axis

ylabel('True Positive Rate'); %%label on y axistitle('ROC for Mean Path Length'); %%title of graph

Thanks in advance for your help.

Answer 1

[Subhadeep Koley]

Hi, you can use the 'Sheet' Name-Value pair to specify the sheet you want to read data from.

Additionally, using a for loop, you can loop through the various sheets of the Excel file to plot the ROC curves.

rocTable = readtable('ROC.xlsx', 'Sheet', 'BM', 'range', '$A1:$D17');

Hope this helps!