F度量提供的值太小

Question

F量度表示为：（2 * Precision * Recall /（Precision + Recall）。

我在Matlab中将其称为：

clc;
clear all;
close all;
% images = uigetdir('F:\images ..','Select Image Folder');
images = uigetdir('F:\images ..','Select Image Folder');
fnames=dir(images);
f=filesep;
groundtruth= uigetdir('F:\groundtruth...','Select GroundTruth Folder');
names=dir(groundtruth);
A={'.jpg','.bmp','.png','.tif'};
tic;
for k = 1:length(fnames)
[pathstr,name,ext] = fileparts(fnames(k).name);
    if strcmpi(ext,'.jpg')==1;
    rgb=imread([images,filesep,...
    fnames(k).name]);
        if(size(rgb,3) > 1)
             f=rgb2gray(rgb); 
        else
             f=rgb;
        end
    sprintf('%d',k)
    t1=imread([groundtruth,filesep,...
    names(k).name]);
    sprintf('%d',k)   
c = edge(f,'canny', 0.1);

idx = (t1()==1);
pc = length(t1(idx));
nc = length(t1(~idx));
Nc = pc+nc;

tpc = sum(t1(idx)==c(idx));
tnc = sum(t1(~idx)==c(~idx));
fpc = nc-tnc;
fnc = pc-tpc;

tp_ratec = tpc/pc;
tn_ratec = tnc/nc;

accuracyc = (tpc+tnc)/Nc;
sensitivityc = tp_ratec;
specificityc = tn_ratec;
precisionc = tpc/(tpc+fpc);
recallc = sensitivityc;
f_measurec = 2*((precisionc*recallc)/(precisionc + recallc));
gmeanc = sqrt(tp_ratec*tn_ratec);

当我计算它时，我得到的F值太小。

怎么了？

此F度量的资源（图像和免费）在这里： https://www2.eecs.berkeley.edu/Research/Projects/CS/vision/bsds/ https://www2.eecs.berkeley.edu/Research/Projects/CS/vision/grouping/papers/amfm_pami2010.pdf

F1 Score vs ROC AUC