graphc: 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 CentOS possible default full paths are:

/usr/bin/graphc - from package: ncl

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/graphc - from package: ncl-ncarg

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

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