histogram: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/cmtk/bin/histogram - from package: cmtk

You may install the required package with command apt-get install {package}

Error in other languages:
histogram: bevel nie gevind nie
histogram: comandă negăsită
histogram: comando não encontrado
histogram: commande introuvable
histogram: command not found
histogram: käsku ei ole
histogram: không tìm thấy lệnh
histogram: komanda nerasta
histogram: Kommando nicht gefunden.
histogram: kommandot finns inte
histogram: komut yok
histogram: nie znaleziono polecenia
histogram: níor aimsíodh an t-ordú
histogram: no se encontró la orden
histogram: no s'ha trobat l'ordre
histogram: opdracht niet gevonden
histogram: parancs nem található
histogram: perintah tidak ditemukan
histogram: príkaz nenájdený
histogram: příkaz nenalezen
histogram: команда не найдена
histogram: командата не е открита
histogram: 命令找不到
histogram: コマンドが見つかりません