In a certain city, in 1970, the inhabitants under the age of 15 are 18%, those with at least 15 years and under 25  16.5%, those with at least 25 and under 55  50%, those with at least 55 and less than 65  10%, those with at least 65  5.5%.

Sull'asse verticale è rappresentata la frequenza percentuale unitaria (o densità)
On the y axis, the unitary percentage frequency (or density) is represented
(that is the percentage frequencies divided by the amplitude of each interval).
You can round mean (taking into account the width of the intervals).

Puoi aprire il codice e modificare la funzione
You can open the Code and modify the function

// I: estremi degli intervalli, P: frequenze
I=[0,   5,  10,  20,  30,  40,  50,  60,  75,  100]
P=[ 729, 35,  77, 132, 134, 285, 457, 1401, 1569]
NP=P.length; SUM=0; for(i=0;i<NP;i=i+1)  {SUM=SUM+P[i]}
mean=0; for(i=0;i<NP;i=i+1) {mean=mean+P[i]*(I[i]+I[i+1])/2}; mean=mean/SUM
Tot=0; for(i=0;i<NP;i=i+1) {Tot=Tot+P[i]}; for(i=0;i<NP;i=i+1) {P[i]=P[i]/Tot/(I[i+1]-I[i])}
LLx=[]; j=0; for(i=1;i<=NP;i=i+1) { LLx[j]=I[i-1]; LLx[j+1]=I[i-1]; LLx[j+2]=I[i]; LLx[j+3]=I[i]; j=j+4 }
LLy=[]; j=0; for(i=1;i<=NP;i=i+1) { LLy[j]=0; LLy[j+1]=P[i-1]; LLy[j+2]=P[i-1]; LLy[j+3]=0; j=j+4 }

aX = 0; bX = 100
aY = 0; bY = 2/100
Dx = 10; Dy = 0.1/100
YY = [0.5/100,1/100,1.5/100,2/100]
XX=[50]
...
yy=YY; xx=XX
C1="black"
L1x=LLx; L1y=LLy
...
AX=BX=AY=BY=""
AAX=aX; BBX=bX; AAY=aY; BBY=bY
...