plotdrop: 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/plotdrop - from package: plotdrop

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

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