Calculating local minima locations adjacent to a local maxima

I m trying to find following points corresponding to local maximum.

For this I am writing a following code

url='https://i.ytimg.com/vi/9wnO8jQniS0/hqdefault.jpg';
Image=imread(url);
grayImage=rgb2gray(Image);
edgedImage=edge(grayImage,'sobel','vertical');
signal=sum(edgedImage,2);
plot(signal);
window=10;
h=gausswin(2*window+1)./window;
smSignal=filter(h,1,signal);
figure;plot(smSignal)

How would I find those points locations on x-axis? Also if I set some threshold like peaks with height greater than 40 only then how only those minpoint corresponding to peaks greater than 40 will be selected?