documentclass{article}
usepackage{tikz}
usepackage{pgfplots}

begin{document}
begin{tikzpicture}
begin{axis}[
  xbar stacked,
  bar width=15pt,
  xlabel={Number of total errors $|$ Bars: incorrectly predicted class},
  ylabel={Target class},
  yticklabels={E,T,M,N,A,6/W,O,K,R,S,7,F,I,1,3,G,X,4,5,B,H},
  symbolic y coords={E,T,M,N,A,6/W,O,K,R,S,7,F,I,1,3,G,X,4,5,B,H},
  xtick={0,2,4,6,8,10,12,14,16,18},
  ytick=data,
  width=12.2cm,
  height=7.1cm,
  axis y line*=none,
  axis x line*=bottom,
  ]
addplot[fill=gray!50!black,draw=black] coordinates {(5,E) (8,T) (8,M) (5,N) (3,A) (6,6/W) (5,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(4,E) (6,T) (3,M) (2,N) (3,A) (1,6/W) (1,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(3,E) (1,T) (2,M) (2,N) (2,A) (0,6/W) (1,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(2,E) (1,T) (1,M) (1,N) (1,A) (0,6/W) (0,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(1,E) (0,T) (0,M) (1,N) (1,A) (0,6/W) (0,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(1,E) (0,T) (0,M) (0,N) (0,A) (0,6/W) (0,O)};
addplot[fill=gray!50!black,draw=black] coordinates {(1,E) (0,T) (0,M) (0,N) (0,A) (0,6/W) (0,O)};

coordinate (ES) at (-10,0);
coordinate (EM) at (16mm,0);
coordinate (ET) at (41mm,0);
coordinate (EH) at (60mm,0);
coordinate (EA) at (72.8mm,0);
coordinate (EO) at (79mm,0);
coordinate (EP) at (85.3mm,0);

coordinate (TA) at (-10,7.5mm);
coordinate (TS) at (34.7mm,7.5mm);
coordinate (TE) at (72.8mm,7.5mm);
coordinate (TN) at (79mm,7.5mm);

coordinate (MN) at (-10,15.5mm);
coordinate (MT) at (34.7mm,15.5mm);
coordinate (MA) at (54mm,15.5mm);
coordinate (MS) at (66.6mm,15.5mm);

coordinate (NM) at (-10,23.1mm);
coordinate (NA) at (16mm,23.1mm);
coordinate (NH) at (28.5mm,23.1mm);
coordinate (NT) at (41mm,23.1mm);
coordinate (NY) at (47.4mm,23.1mm);

coordinate (AE) at (-10,30.8mm);
coordinate (AN) at (3.2mm,30.8mm);
coordinate (AM) at (22.1mm,30.8mm);
coordinate (AP) at (34.7mm,30.8mm);
coordinate (AT) at (41mm,30.8mm);

coordinate (6W7) at (-10,38.2mm);
coordinate (6W3) at (22.1mm,38.2mm);

coordinate (OE) at (-10,46mm);
coordinate (O3) at (16mm,46mm);
coordinate (OC) at (22.1mm,46mm);

end{axis}
node[style={text=white}] at (ES) {S};
node[style={text=white}] at (EM) {M};
node[style={text=white}] at (ET) {T};
node[style={text=white}] at (EH) {H};
node[style={text=white}] at (EA) {A};
node[style={text=white}] at (EO) {O};
node[style={text=white}] at (EP) {P};

node[style={text=white}] at (TA) {A};
node[style={text=white}] at (TS) {S};
node[style={text=white}] at (TE) {E};
node[style={text=white}] at (TN) {N};

node[style={text=white}] at (MN) {N};
node[style={text=white}] at (MT) {T};
node[style={text=white}] at (MA) {A};
node[style={text=white}] at (MS) {S};

node[style={text=white}] at (NM) {M};
node[style={text=white}] at (NA) {A};
node[style={text=white}] at (NH) {H};
node[style={text=white}] at (NT) {T};
node[style={text=white}] at (NY) {Y};

node[style={text=white}] at (AE) {E};
node[style={text=white}] at (AN) {N};
node[style={text=white}] at (AM) {M};
node[style={text=white}] at (AP) {P};
node[style={text=white}] at (AT) {T};

node[style={text=white}] at (6W7) {7};
node[style={text=white}] at (6W3) {3};

node[style={text=white}] at (OE) {E};
node[style={text=white}] at (O3) {3};
node[style={text=white}] at (OC) {C};
end{tikzpicture}
end{document}