mummerplot: 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/bin/mummerplot - from package: mummer

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

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